Recombinant Chlorokybus atmophyticus NAD (P)H-quinone oxidoreductase subunit 3, chloroplastic

What is the basic function of NAD(P)H-quinone oxidoreductase in Chlorokybus atmophyticus?

NAD(P)H-quinone oxidoreductases (NDH) in Chlorokybus atmophyticus, like those in other organisms, catalyze the two-electron transfer from NAD(P)H to quinones without an energy-transducing component. Type II NDH-2 enzymes regenerate NAD(P)+ in metabolic pathways, participating in respiratory electron transport chains in chloroplasts. Unlike their Type I counterparts, they do not contribute to proton translocation across membranes, functioning solely for electron transfer . In Chlorokybus atmophyticus, this protein is localized in the chloroplast, suggesting its involvement in photosynthetic electron transport rather than mitochondrial respiration.

How does the structure of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase differ from other charophytic algae?

While specific structural information for the Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase subunit 3 is limited, research on NDH-2 enzymes reveals significant variation across species. Traditional NDH-2 enzymes contain noncovalently bound FAD as cofactors, but recent discoveries show variants with covalently bound FMN or noncovalently bound FMN replacing FAD . Chlorokybus atmophyticus, as an early-diverging charophyte, likely possesses distinctive structural features that reflect its evolutionary position. The protein typically contains two ADP-binding sites, and some variants also display EF-hand motifs for calcium binding . Comparative structural analysis among charophytic algae would require protein crystallography studies and sequence alignments to determine conservation patterns and unique elements.

What are the optimal conditions for expressing recombinant Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase?

The expression of recombinant Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase subunit 3 requires specific conditions for optimal yield and activity. Based on protocols for similar proteins, a methodological approach would include:

• Vector selection: Choose expression vectors with strong promoters compatible with the host system (bacterial, yeast, or insect cells).

• Codon optimization: Adapt the coding sequence to the codon usage bias of the expression host.

• Growth conditions: For Chlorokybus atmophyticus cultivation, use soil medium (JM:SE2, 7:3) at 24°C under constant low light .

• Purification strategy: Implement affinity chromatography with histidine tags, followed by size-exclusion chromatography.

• Buffer optimization: Test various buffer compositions (typically HEPES-KOH, pH 7.5 with 2 mM MgCl₂) to maintain protein stability and activity.

• Storage conditions: Determine optimal storage parameters to prevent degradation and maintain enzyme activity.

Commercial suppliers like CUSABIO TECHNOLOGY LLC have established protocols for producing this recombinant protein , though researchers developing their own expression systems should optimize conditions through systematic testing of temperature, inducer concentration, and incubation time.

How can researchers effectively isolate and purify NAD(P)H-quinone oxidoreductase from Chlorokybus atmophyticus chloroplasts?

Isolation and purification of NAD(P)H-quinone oxidoreductase from Chlorokybus atmophyticus chloroplasts requires a systematic approach:

• Chloroplast isolation: Begin with cell culture grown to mid-log phase (approximately 4th hour in the light phase). Harvest cells by centrifugation at 4,000 × g for 10 minutes. Extract intact chloroplasts following established protocols using sucrose buffer A (50 mM HEPES-KOH, pH 7.5; 2 mM MgCl₂) and sucrose buffer B .

• Membrane fractionation: Separate thylakoid membranes from chloroplast envelope membranes through differential centrifugation. Since NAD(P)H-quinone oxidoreductase may be partially associated with envelope membranes rather than thylakoids, careful fractionation is essential.

• Protein extraction: Solubilize membrane proteins using mild detergents (n-dodecyl-β-D-maltoside or digitonin) at optimized concentrations.

• Purification steps:

  • Anion exchange chromatography

  • Affinity chromatography using NAD(P)H analogs as ligands

  • Size exclusion chromatography for final polishing

• Activity verification: Assess enzyme activity through spectrophotometric assays measuring NAD(P)H oxidation in the presence of quinone substrates.

The purification must be performed at 4°C with protease inhibitors to prevent degradation. Western blotting with specific antibodies can confirm the presence of the target protein in each fraction.

What enzymatic assays are most reliable for measuring the activity of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase?

Several reliable enzymatic assays can be employed to measure the activity of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase, each with specific advantages:

• Spectrophotometric NAD(P)H oxidation assay:

  • Monitor the decrease in absorbance at 340 nm corresponding to NAD(P)H oxidation

  • Reaction buffer: 50 mM HEPES-KOH (pH 7.5), 2 mM MgCl₂

  • Substrate concentrations: 100 μM NAD(P)H and 50 μM ubiquinone or plastoquinone

  • Reaction rate calculated using the extinction coefficient of NAD(P)H (6,220 M⁻¹cm⁻¹)

• Artificial electron acceptor assays:

  • Use dichlorophenolindophenol (DCPIP) as an electron acceptor

  • Monitor reduction at 600 nm

  • Useful for distinguishing between Type I and Type II NAD(P)H oxidoreductases

• Reverse electron transfer assay:

  • Measure quinol oxidation coupled to NAD(P)⁺ reduction

  • Particularly important at alkaline pH where NADPH oxidation may be prevented by electrostatic repulsion between the phosphate group and membrane phospholipids

• Inhibitor sensitivity profiles:

  • Test insensitivity to rotenone (characteristic of Type II enzymes)

  • Differential sensitivity to flavonoids and quinone analogs

When conducting these assays, researchers should consider the pH dependence of the enzyme activity, as alkaline conditions may affect NADPH oxidation due to electrostatic repulsion between the phosphate group of NADPH and membrane phospholipids .

How is the NAD(P)H-quinone oxidoreductase from Chlorokybus atmophyticus evolutionarily related to those from other photosynthetic organisms?

The evolutionary relationship of NAD(P)H-quinone oxidoreductase from Chlorokybus atmophyticus to those from other photosynthetic organisms reflects the organism's position as an early-diverging charophyte alga. Phylogenetic analysis reveals several key evolutionary patterns:

• Ancestral features: As a basal charophyte, Chlorokybus atmophyticus likely retains ancestral features of NAD(P)H-quinone oxidoreductases that were present in the common ancestor of charophytes and land plants.

• Evolutionary transitions: The protein serves as a crucial marker for understanding the evolution of photosynthetic electron transport during the transition from aquatic algae to land plants.

• Comparative analysis: When aligned with homologs from other streptophyte algae (Klebsormidium, Coleochaete, Chara) and land plants, the protein shows sequence conservation in functional domains while diverging in regulatory regions .

• Cofactor evolution: The presence of specific cofactors (FAD vs. FMN) and their binding modes (covalent vs. non-covalent) represents an important evolutionary marker in the diversification of these enzymes .

Methodologically, researchers can reconstruct these evolutionary relationships through maximum likelihood phylogenetic analyses of protein sequences, complemented by comparative genomics to identify synteny and gene family expansion/contraction events across the streptophyte lineage.

What can Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase tell us about the evolution of photosynthetic electron transport chains?

Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase subunit 3 provides valuable insights into the evolution of photosynthetic electron transport chains, particularly during the transition from aquatic to terrestrial environments:

• Evolutionary intermediates: As an early-diverging charophyte, Chlorokybus atmophyticus represents a crucial evolutionary step between chlorophyte algae and land plants. Its NAD(P)H-quinone oxidoreductase serves as a molecular fossil that preserves features of ancestral electron transport systems while showing innovations that later became standard in land plants.

• Alternative electron transport pathways: Type II NAD(P)H:quinone oxidoreductases catalyze the two-electron transfer from NAD(P)H to quinones without energy transduction , suggesting they participate in alternative electron flows that may have been critical during the evolutionary adaptation to fluctuating light conditions in early land plants.

• Redox balance mechanisms: The enzyme's ability to oxidize both NADH and NADPH provides flexibility in maintaining cellular redox balance, potentially representing an adaptation to the environmental fluctuations encountered during terrestrialization.

• Cofactor evolution: The transition from FAD to FMN as cofactors in some NDH-2 enzymes represents a significant evolutionary innovation that may correlate with functional specialization of these proteins during plant evolution.

• Regulatory adaptations: The presence of additional regulatory domains, such as calcium-binding EF-hand motifs in some NDH-2 enzymes , indicates the evolution of sophisticated regulatory mechanisms to coordinate electron transport with other cellular processes.

Methodologically, researchers can investigate these evolutionary questions through ancestral sequence reconstruction, site-directed mutagenesis to test the functional importance of conserved residues, and comparative biochemistry across the charophyte-to-land plant transition.

How can yeast two-hybrid screening be optimized to identify interaction partners of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase?

Optimizing yeast two-hybrid screening to identify interaction partners of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase requires careful consideration of several methodological aspects:

• Bait construct design:

  • Remove chloroplast transit peptide sequences by using CrPCYA1ΔTP (amino acids 56-556) or equivalent domains

  • Test different functional domains separately (N-terminal, core catalytic domain, C-terminal extension) to prevent masking of interaction surfaces

  • Clone the coding region into a pBD-GAL4 vector for expression as a fusion with the DNA-binding domain

• Autoactivation testing:

  • Verify that the bait construct alone does not activate reporter genes by testing growth on selective media lacking histidine (SD-Trp-His)

  • If autoactivation occurs, modify the construct to remove the activating region or add 3-amino-1,2,4-triazole (3-AT) to increase selection stringency

• Library preparation:

  • Construct a high-quality cDNA library from Chlorokybus atmophyticus grown under various conditions to capture the full expression profile

  • Use sequential transformation: first transform the bait construct, then the cDNA library

• Screening conditions:

  • Plate transformed yeast cells on selective media lacking tryptophan, leucine, and histidine (SD-Trp-Leu-His)

  • Incubate at 28°C for 2-4 days before colony selection

  • Include proper controls with known interactors and non-interactors

• Confirmation of positive interactions:

  • Isolate plasmids from positive colonies and retransform into fresh yeast cells with the bait to confirm interaction

  • Use additional methods such as co-immunoprecipitation or bimolecular fluorescence complementation to validate interactions in vivo

For Chlorokybus atmophyticus proteins specifically, optimizing expression conditions is crucial since these proteins may not fold properly at standard yeast growth temperatures. Consider lowering incubation temperature to 20-24°C to match the native growth conditions of Chlorokybus atmophyticus .

What approaches are most effective for studying the localization of NAD(P)H-quinone oxidoreductase within Chlorokybus atmophyticus cells?

Studying the subcellular localization of NAD(P)H-quinone oxidoreductase within Chlorokybus atmophyticus cells requires a multi-faceted approach:

• Cellular fractionation:

  • Isolate intact chloroplasts following established protocols for charophyte algae

  • Further fractionate chloroplasts into envelope membranes, thylakoid membranes, and stroma

  • Process cells at the 4th hour in the light phase for optimal chloroplast integrity

  • Use differential centrifugation with sucrose buffer A (50 mM HEPES-KOH, pH 7.5; 2 mM MgCl₂) and sucrose buffer B

  • Analyze fractions by western blotting with antibodies against the target protein

• Fluorescent protein fusions:

  • Generate constructs expressing the protein fused to fluorescent reporters (GFP, YFP)

  • Introduce constructs through established transformation protocols

  • Observe localization using confocal microscopy with appropriate chlorophyll autofluorescence controls

  • Consider photoconvertible fluorescent proteins to track protein movement between compartments

• Immunogold electron microscopy:

  • Fix Chlorokybus atmophyticus cells using high-pressure freezing for optimal ultrastructure preservation

  • Perform immunolabeling with specific antibodies against NAD(P)H-quinone oxidoreductase

  • Visualize using transmission electron microscopy to achieve nanometer-scale resolution of protein localization

• Predictive analysis:

  • Use in silico tools to identify potential targeting sequences (chloroplast transit peptides, membrane-spanning domains)

  • Compare with experimental data from model organisms

• Dynamic localization studies:

  • Track changes in protein distribution under different light conditions, developmental stages, or stress treatments

  • Combine with activity assays to correlate localization with function

The protein may be partially associated with chloroplast envelope membranes while absent from thylakoid membranes , requiring careful separation and analysis of these distinct compartments.

How can researchers effectively study the post-translational modifications of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase?

Studying post-translational modifications (PTMs) of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase requires a comprehensive workflow combining multiple analytical approaches:

• Protein purification and enrichment:

  • Isolate the recombinant protein using affinity tags or purify from native sources

  • Enrich specific PTM forms using dedicated enrichment techniques (e.g., titanium dioxide for phosphopeptides, lectin affinity for glycosylation)

  • Separate protein isoforms by 2D gel electrophoresis to identify charge or size variants

• Mass spectrometry analysis:

  • Perform tryptic digestion followed by LC-MS/MS analysis

  • Implement parallel reaction monitoring (PRM) or multiple reaction monitoring (MRM) for targeted analysis of specific modifications

  • Use electron-transfer dissociation (ETD) or electron-capture dissociation (ECD) fragmentation methods to preserve labile modifications

  • Search data against PTM databases with appropriate parameters for phosphorylation, acetylation, methylation, and other modifications

• Site-specific analysis:

  • Generate site-directed mutants of predicted modification sites to assess their functional importance

  • Develop modification-specific antibodies for western blotting and immunoprecipitation

  • Use phosphatase or deacetylase treatments to confirm the identity of modifications

• Functional impact assessment:

  • Compare enzyme kinetics of modified versus unmodified protein forms

  • Analyze how modifications affect protein-protein interactions, particularly with potential partners identified through methods like yeast two-hybrid screening

  • Investigate the relationship between PTMs and localization within chloroplast subcompartments

• Structural analysis:

  • Model the structural consequences of PTMs using in silico approaches

  • When possible, determine crystal structures of modified protein forms

For NDH-2 enzymes specifically, researchers should focus on modifications that might affect cofactor binding (FAD or FMN), as variations in cofactor utilization have been documented in this enzyme family . Additionally, the potential presence of calcium-binding EF-hand motifs suggests that calcium-dependent regulation might be relevant to investigate.

How does Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase contribute to stress responses in extreme environments?

The role of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase in stress responses likely involves complex redox regulatory mechanisms:

• Oxidative stress management:

  • The enzyme may serve as an alternative electron sink during high light stress, preventing over-reduction of the photosynthetic electron transport chain

  • By maintaining NAD(P)+/NAD(P)H ratios, it could regulate cellular redox state during stress conditions

  • Similar to findings in other photosynthetic organisms, it may participate in bilin-mediated retrograde signaling pathways that mitigate oxidative stress during dark-to-light transitions

• Temperature adaptation mechanisms:

  • As an early-diverging charophyte, Chlorokybus atmophyticus may possess unique adaptations for temperature fluctuations

  • The enzyme's activity and stability across temperature ranges could be assessed using differential scanning calorimetry and temperature-dependent enzyme kinetics

  • Comparative analysis with orthologs from thermophilic and psychrophilic organisms would reveal adaptive features

• Methodological approaches:

  • Expose cultures to controlled stress conditions (high light, temperature extremes, nutrient limitation)

  • Monitor changes in protein abundance, post-translational modifications, and enzymatic activity

  • Perform RNA-seq analysis to identify co-regulated genes in stress response networks

  • Develop knockout or knockdown systems to assess phenotypic consequences under stress conditions

• Cross-talk with signaling pathways:

  • Investigate potential interactions with calcium signaling, given that some NDH-2 enzymes contain calcium-binding EF-hand motifs

  • Examine relationships with retrograde signaling pathways using specific inhibitors and genetic approaches

Understanding these stress response mechanisms may provide insights into evolutionary adaptations during the transition from aquatic to terrestrial environments and reveal novel strategies for engineering stress tolerance in crops.

What role might Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase play in the regulation of chlorophyll biosynthesis?

The potential role of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase in chlorophyll biosynthesis regulation represents an intriguing research direction:

• Protein-protein interaction networks:

  • Evidence from related algal species suggests that ferredoxin-dependent enzymes can directly interact with the rate-limiting chlorophyll biosynthetic enzyme LPOR (light-dependent protochlorophyllide oxidoreductase)

  • Similar interactions might exist in Chlorokybus atmophyticus, potentially forming regulatory complexes that coordinate electron transport with pigment synthesis

  • Such interactions could be species-specific, as homologous proteins from Arabidopsis do not interact with each other

• Redox regulation mechanisms:

  • NAD(P)H-quinone oxidoreductase influences cellular redox state through NAD(P)H oxidation

  • Chlorophyll biosynthesis enzymes are known to be redox-regulated, suggesting a potential regulatory connection

  • The enzyme may participate in a feedback loop where chlorophyll levels influence electron transport, which in turn regulates chlorophyll synthesis

• Retrograde signaling pathways:

  • Bilin pigments (products of heme degradation) function as essential retrograde signals during dark-to-light transitions

  • These signals are required for chlorophyll accumulation and maintenance of functional photosynthetic apparatus

  • NAD(P)H-quinone oxidoreductase may influence this signaling pathway through effects on electron transport and redox homeostasis

• Experimental approaches:

  • Yeast two-hybrid screening to identify interactions with chlorophyll biosynthesis enzymes

  • Co-immunoprecipitation and bimolecular fluorescence complementation to validate interactions in vivo

  • Analysis of chlorophyll biosynthesis in knockdown or knockout mutants of NAD(P)H-quinone oxidoreductase

  • In vitro reconstitution of enzyme complexes to study direct regulatory effects

These investigations could reveal novel regulatory mechanisms connecting electron transport, redox homeostasis, and chlorophyll biosynthesis in early-diverging charophytes, with potential implications for understanding the evolution of photosynthetic apparatus regulation.

What are the implications of NAD(P)H-quinone oxidoreductase research in Chlorokybus atmophyticus for understanding the evolution of bioenergetic systems?

Research on NAD(P)H-quinone oxidoreductase in Chlorokybus atmophyticus has profound implications for understanding the evolution of bioenergetic systems:

• Evolutionary transition markers:

  • Chlorokybus atmophyticus, as an early-diverging charophyte, occupies a critical position in the evolutionary lineage leading to land plants

  • Its NAD(P)H-quinone oxidoreductase represents an evolutionary intermediate that can reveal how electron transport chains adapted during the transition from aquatic to terrestrial environments

  • Comparative analysis with homologs from chlorophytes, other charophytes, and land plants can reconstruct the stepwise evolution of these systems

• Alternative electron transport pathways:

  • Type II NAD(P)H:quinone oxidoreductases catalyze electron transfer without contributing to proton translocation

  • These alternative pathways may have been crucial for adaptation to fluctuating light conditions and other environmental stresses during land colonization

  • Understanding their regulation and integration with the main electron transport chain illuminates evolutionary strategies for maintaining redox balance

• Methodological approaches for evolutionary studies:

  • Ancestral sequence reconstruction to infer properties of ancient enzymes

  • Heterologous expression of reconstructed ancestral proteins to test their biochemical properties

  • Phylogenetic analyses incorporating structural and functional data

  • Comparative genomics across the chlorophyte-charophyte-embryophyte transition

• Implications for synthetic biology:

  • Understanding the modular nature of electron transport components in an evolutionary context

  • Potential for engineering novel electron transport pathways with desired properties

  • Insights into minimal requirements for functional electron transport systems

• Connection to organellar evolution:

  • The chloroplastic localization of this enzyme provides insights into the specialization of organellar function during plant evolution

  • Studying its interactions with other chloroplast proteins reveals co-evolutionary patterns

  • Potential role in the evolution of retrograde signaling systems between chloroplast and nucleus

This research contributes to our fundamental understanding of how complex bioenergetic systems evolved and diversified, potentially revealing design principles that could inspire biotechnological applications in renewable energy generation and crop improvement.

What are the critical factors to consider when designing expression constructs for Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase?

When designing expression constructs for Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase, researchers should consider several critical factors:

• Domain structure analysis:

  • Remove the transit peptide sequence (approximately the first 55 amino acids) for expression in non-chloroplast systems

  • Consider expressing distinct functional domains separately:

    • N-terminal extension (NTE)

    • Core catalytic FDBR (ferredoxin-dependent biliverdin reductase) domain

    • C-terminal extension (CTE)

  • The conserved FDBR domain may be sufficient for minimal function, as seen in similar proteins

• Expression vector selection:

  • Choose vectors with appropriate promoters for the host system

  • For yeast two-hybrid studies, vectors like pBD-GAL4 have proven effective

  • For protein production, consider inducible systems with tight regulation

• Fusion tag strategies:

  • N-terminal His-tag or GST-tag for purification

  • Consider the impact of tags on protein folding and activity

  • Include protease cleavage sites for tag removal if necessary

  • For localization studies, C-terminal fluorescent protein tags may be appropriate

• Codon optimization:

  • Adapt the coding sequence to the codon usage bias of the expression host

  • Consider GC content and potential secondary structures in mRNA

• Special considerations:

  • Include appropriate flanking sequences for efficient translation initiation

  • Design multiple constructs with varying N- and C-termini to optimize expression and solubility

  • For structural studies, consider surface entropy reduction mutations to facilitate crystallization

When testing constructs, perform small-scale expression trials to optimize induction conditions, temperature, and harvest time before scaling up production. Western blotting and activity assays should be employed to confirm that the recombinant protein is correctly folded and functional.

How can researchers address the challenges of protein instability when working with recombinant Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase?

Addressing protein instability challenges when working with recombinant Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase requires systematic optimization of multiple parameters:

• Buffer composition optimization:

  • Test various buffer systems (HEPES, Tris, phosphate) at pH ranges 6.5-8.0

  • Include stabilizing agents like glycerol (10-20%) to prevent aggregation

  • Add reducing agents (DTT, β-mercaptoethanol) to maintain thiol groups

  • For membrane-associated proteins, include appropriate detergents (n-dodecyl-β-D-maltoside, digitonin) at concentrations above their critical micelle concentration

• Temperature management:

  • Perform all purification steps at 4°C

  • Consider native environmental conditions: Chlorokybus atmophyticus grows optimally at 24°C under constant low light

  • Test protein stability at various temperatures using differential scanning fluorimetry

• Cofactor retention strategies:

  • Supplement buffers with FAD or FMN to prevent cofactor dissociation

  • Type II NAD(P)H:quinone oxidoreductases typically contain noncovalently bound FAD, though some variants use FMN instead

  • Monitor cofactor retention spectrophotometrically

• Protease inhibition:

  • Include a comprehensive protease inhibitor cocktail during extraction and purification

  • Consider specific inhibitors based on proteolytic susceptibility analysis

  • Minimize sample handling and exposure time during purification

• Storage optimization:

  • Test protein stability in various storage conditions (4°C, -20°C, -80°C)

  • Evaluate cryoprotectants (glycerol, sucrose, trehalose) at different concentrations

  • Consider flash-freezing in liquid nitrogen with appropriate stabilizing agents

  • Assess activity retention after freeze-thaw cycles

• Expression strategies:

  • Express stable subdomains if the full-length protein proves recalcitrant

  • Consider fusion partners known to enhance solubility (MBP, SUMO, thioredoxin)

  • Co-express with chaperones to improve folding efficiency

• Protein engineering approaches:

  • Identify and mutate surface-exposed hydrophobic residues

  • Introduce stabilizing disulfide bonds based on structural predictions

  • Remove flexible loops that may contribute to instability

Each optimization step should be evaluated through activity assays to ensure that stabilization does not compromise the protein's functional properties.

What bioinformatics approaches are most valuable for analyzing the structure-function relationships of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase?

Bioinformatics approaches provide valuable insights into structure-function relationships of Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase without requiring extensive experimental work:

• Sequence analysis and domain prediction:

  • Identify functional domains using tools like Pfam, SMART, and InterPro

  • Detect conserved motifs characteristic of NAD(P)H-binding sites and quinone-binding regions

  • Search for regulatory elements such as calcium-binding EF-hand motifs, which occur in some NDH-2 enzymes

  • Analyze the transit peptide using ChloroP or TargetP to confirm chloroplast localization

• Multiple sequence alignment and evolutionary analysis:

  • Align the sequence with homologs from diverse organisms

  • Identify conserved residues that may be functionally critical

  • Calculate conservation scores to pinpoint catalytically important regions

  • Construct phylogenetic trees to understand evolutionary relationships

  • Perform ancestral sequence reconstruction to infer properties of evolutionary intermediates

• Structural modeling and analysis:

  • Generate homology models using tools like SWISS-MODEL, Phyre2, or AlphaFold2

  • Validate models through molecular dynamics simulations

  • Dock substrates (NAD(P)H, quinones) to predict binding modes

  • Analyze electrostatic surface potential to understand substrate preferences

  • At alkaline pH, electrostatic repulsion between NADPH's phosphate group and membrane phospholipids may affect activity

• Functional site prediction:

  • Identify potential catalytic residues using tools like ConSurf and POOL

  • Predict post-translational modification sites

  • Analyze protein-protein interaction interfaces

  • Map conservation onto structural models to visualize functional hotspots

• Integrative approaches:

  • Combine sequence-based predictions with available experimental data

  • Use co-evolution analysis to predict residue contacts

  • Implement machine learning approaches to classify functional properties

These computational approaches can guide experimental design by identifying targets for site-directed mutagenesis, predicting biochemical properties, and providing hypotheses about evolutionary adaptations in Chlorokybus atmophyticus NAD(P)H-quinone oxidoreductase.