Recombinant Ajellomyces capsulata 3-ketoacyl-CoA reductase (HCAG_07127)

How is the recombinant protein produced for research purposes?

The recombinant full-length Ajellomyces capsulata 3-ketoacyl-CoA reductase is typically produced using bacterial expression systems. According to available product information, the protein (residues 1-339) is expressed in E. coli with an N-terminal His-tag to facilitate purification . The expression construct contains the complete coding sequence of the HCAG_07127 gene, allowing for production of the full-length protein with the His-tag fusion.

The general methodology includes:

• Cloning the coding sequence into a bacterial expression vector

• Transformation into a suitable E. coli strain

• Induction of protein expression under optimized conditions

• Cell lysis and protein extraction

• Purification using nickel affinity chromatography (utilizing the His-tag)

• Quality control assessment (typically SDS-PAGE with >90% purity)

• Lyophilization for long-term stability

What are the optimal storage and reconstitution protocols?

For optimal experimental outcomes, proper storage and reconstitution of the recombinant protein are essential:

Prior to reconstitution, the vial should be briefly centrifuged to bring contents to the bottom. For experimental applications requiring multiple uses, creating working aliquots stored at 4°C is advised, while maintaining master stocks at -20°C/-80°C .

How can enzyme activity be reliably measured in experimental settings?

Measuring 3-ketoacyl-CoA reductase activity requires careful experimental design that monitors either substrate consumption or product formation. While specific assay conditions for the Ajellomyces capsulata enzyme aren't directly provided in the search results, the following general methodology can be adapted:

• Spectrophotometric NADPH oxidation assay:

  • Prepare reaction buffer (typically phosphate buffer, pH 7.0-7.5)

  • Add NADPH (typically 100-200 μM)

  • Add 3-ketoacyl-CoA substrate (concentration range 10-100 μM)

  • Add purified recombinant enzyme (0.1-1 μg)

  • Monitor decrease in absorbance at 340 nm (indicating NADPH oxidation)

  • Calculate enzyme activity based on NADPH consumption rate

• Alternative product detection methods:

  • HPLC analysis of 3-hydroxyacyl-CoA formation

  • Coupled enzyme assays that link product formation to a colorimetric change

  • LC-MS detection of substrate consumption and product formation

When designing these assays, researchers should consider buffer composition, pH optimization, temperature sensitivity, and potential inhibitors or activators that might affect enzyme kinetics.

What experimental approaches can detect protein-protein interactions involving this enzyme?

Understanding the interactome of 3-ketoacyl-CoA reductase in Ajellomyces capsulata provides insight into its regulation and functional integration. Several complementary methods can be employed:

• Co-immunoprecipitation (Co-IP):

  • Prepare fungal cell lysates under non-denaturing conditions

  • Use anti-His antibodies to pull down the recombinant His-tagged protein

  • Identify co-precipitating partners by mass spectrometry

  • Validate interactions with Western blot analysis

• Yeast two-hybrid screening:

  • Use the HCAG_07127 sequence as bait

  • Screen against Ajellomyces capsulata cDNA library

  • Validate positive interactions through additional methods

• Proximity-dependent biotin identification (BioID):

  • Create fusion proteins with promiscuous biotin ligase

  • Express in fungal cells and allow biotinylation of proximal proteins

  • Isolate biotinylated proteins and identify by mass spectrometry

• Protein crosslinking coupled with mass spectrometry:

  • Treat fungal cells or protein mixtures with chemical crosslinkers

  • Digest and analyze by LC-MS/MS

  • Identify cross-linked peptides to map interaction surfaces

The experimental methodology used in reference for studying Histoplasma capsulatum proteome can be adapted for investigating protein-protein interactions, particularly by applying careful protein extraction techniques under non-denaturing conditions.

How does iron availability affect the expression and activity of 3-ketoacyl-CoA reductase?

Research on Histoplasma capsulatum (Ajellomyces capsulata) has demonstrated that iron availability significantly impacts protein expression profiles, including metabolic enzymes. Based on proteomic studies of H. capsulatum under reduced iron conditions:

• Expression changes:

  • When iron availability is reduced (such as through the addition of iron chelators like apo-transferrin), significant alterations occur in the fungal proteome

  • Approximately 3% of detected protein spots show significant changes in abundance in response to iron limitation

  • Many metabolic enzymes show decreased abundance under iron-restricted conditions

• Experimental approach for studying iron effects:

  • Culture H. capsulatum yeast cells in medium at pH 7.5 for 48 hr

  • Switch to medium containing 5 μM apo-transferrin (iron chelator)

  • Harvest cells after 24 hr and 48 hr exposure

  • Perform protein extraction using optimized lysis buffer (9 M urea, 2% CHAPS, 1% DTT, 10 mM protease inhibitor)

  • Analyze protein expression changes using 2D gel electrophoresis

  • Identify proteins by mass spectrometry

While the specific response of 3-ketoacyl-CoA reductase wasn't directly reported, the methodology demonstrates how researchers can investigate the effect of iron restriction on this enzyme's expression and activity, which may have implications for understanding fungal adaptation to host environments where iron is limited as a defense mechanism.

What is the role of 3-ketoacyl-CoA reductase in fungal cell wall synthesis and integrity?

3-Ketoacyl-CoA reductase plays a critical role in fatty acid metabolism, which directly impacts cell membrane composition and indirectly affects cell wall synthesis in pathogenic fungi:

• Metabolic connection:

  • The enzyme catalyzes a key step in fatty acid elongation pathways

  • Long-chain fatty acids produced through this pathway are incorporated into membrane lipids

  • Membrane lipid composition influences cell wall synthesis through several mechanisms:

    • Proper anchoring of cell wall synthesis machinery

    • Precursor transport across the membrane

    • Signaling pathways that regulate cell wall integrity

• Experimental approaches to study this relationship:

  • Gene knockout or RNA interference to reduce enzyme expression

  • Chemical inhibition of enzyme activity

  • Lipidomic analysis of membrane composition changes

  • Microscopic and biochemical assessment of cell wall structure

  • Growth assays under cell wall stress conditions (Congo Red, Calcofluor White)

• Expected phenotypes upon disruption:

  • Altered membrane fluidity

  • Changes in cell wall composition

  • Increased sensitivity to antifungal agents targeting cell wall

  • Potentially reduced virulence in infection models

Understanding these connections provides insight into potential therapeutic approaches targeting fungal metabolism as an alternative to conventional antifungal strategies.

How can Recombinant Ajellomyces capsulata 3-ketoacyl-CoA reductase be utilized in antifungal drug discovery?

The enzymatic activity of 3-ketoacyl-CoA reductase represents a potential target for antifungal drug development due to its essential role in fungal metabolism. Several research approaches can be employed:

• High-throughput inhibitor screening:

  • Develop a miniaturized enzyme activity assay suitable for 96 or 384-well format

  • Screen chemical libraries against the purified recombinant enzyme

  • Identify compounds that inhibit enzyme activity with IC50 determination

  • Confirm specificity by comparing activity against human homologs

• Structure-based drug design:

  • Use the amino acid sequence to generate structural models through homology modeling

  • Alternatively, determine crystal structure of the recombinant protein

  • Perform in silico screening of compound libraries through molecular docking

  • Design rational inhibitors based on enzyme mechanism and active site architecture

• Validation in fungal systems:

  • Test promising inhibitors in cultures of Ajellomyces capsulata

  • Assess growth inhibition, morphological changes, and specific metabolic effects

  • Confirm target engagement through techniques like cellular thermal shift assays

  • Evaluate activity in infection models

• Combination therapy assessment:

  • Test inhibitors in combination with existing antifungals

  • Identify synergistic combinations through checkerboard assays

  • Determine whether targeting this metabolic pathway sensitizes the fungus to other drugs

This research path leverages the availability of recombinant enzyme to establish a pipeline from initial screening to potential therapeutic application.

What genetic and molecular techniques can be used to investigate the role of 3-ketoacyl-CoA reductase in Ajellomyces capsulata virulence?

Understanding the contribution of 3-ketoacyl-CoA reductase to fungal pathogenesis requires sophisticated genetic and molecular approaches:

• Gene disruption strategies:

  • CRISPR-Cas9 mediated gene editing to create knockout mutants

  • RNA interference to achieve conditional knockdown

  • Heterologous complementation to confirm phenotypes

  • Site-directed mutagenesis to create specific enzyme variants

• Expression analysis under infection-relevant conditions:

  • qRT-PCR to quantify transcript levels

  • Western blotting with specific antibodies

  • Proteomic analysis using techniques similar to those described in :

    • Protein extraction using optimized lysis buffer

    • 2D gel electrophoresis for protein separation

    • Identification by mass spectrometry

    • Relative quantification under different conditions

• Infection models:

  • Macrophage infection assays to assess:

    • Adherence and invasion rates

    • Intracellular survival and replication

    • Host cell responses

  • Animal models of histoplasmosis to evaluate:

    • Tissue burden and dissemination

    • Survival rates

    • Histopathological changes

• Omics integration:

  • Combine transcriptomic, proteomic, and metabolomic data

  • Map changes to specific pathways

  • Develop network models of virulence regulation

Research on H. capsulatum has demonstrated methods for studying proteins within activated macrophages, which could be adapted to investigate 3-ketoacyl-CoA reductase specifically .

How does the function of Ajellomyces capsulata 3-ketoacyl-CoA reductase compare with homologous enzymes in other pathogenic fungi?

Comparative analysis of 3-ketoacyl-CoA reductase across fungal species provides evolutionary insights and may reveal species-specific adaptations:

• Sequence comparison approach:

  • Perform BLAST analysis using the Ajellomyces capsulata 3-ketoacyl-CoA reductase sequence

  • Identify homologs in other pathogenic fungi (Paracoccidioides brasiliensis, Blastomyces dermatitidis, Candida spp., etc.)

  • Generate multiple sequence alignments to identify:

    • Conserved catalytic residues

    • Species-specific variations

    • Potential functional domains

• Heterologous expression studies:

  • Express 3-ketoacyl-CoA reductase from different fungal species in a common host

  • Compare enzyme kinetics and substrate preferences

  • Assess differential responses to inhibitors

  • Determine thermal and pH stability profiles

• Structural biology approaches:

  • Generate homology models for different fungal 3-ketoacyl-CoA reductases

  • Compare predicted active sites and binding pockets

  • Identify species-specific features that could be exploited for selective targeting

• Cross-species complementation:

  • Introduce the Ajellomyces capsulata gene into other fungi with disrupted endogenous enzyme

  • Assess the ability to restore wild-type phenotypes

  • Identify species-specific functional requirements

Based on available research, homologs of 3-ketoacyl-CoA reductase have been identified in several pathogenic fungi, including Chaetomium globosum and Coprinopsis cinerea, suggesting evolutionary conservation of this metabolic function . Comparative studies could reveal why certain fungal pathogens are more virulent or adapted to specific host environments.

What are the common technical challenges when working with recombinant fungal enzymes and how can they be addressed?

Working with recombinant fungal enzymes presents several technical challenges that researchers should anticipate:

• Protein solubility issues:

  • Challenge: Recombinant fungal proteins often form inclusion bodies in bacterial expression systems

  • Solutions:

    • Optimize expression temperature (typically lowering to 16-25°C)

    • Use solubility-enhancing fusion tags (SUMO, MBP, TRX)

    • Explore alternative expression hosts (yeast, insect cells)

    • Refold from inclusion bodies using stepwise dialysis

• Post-translational modification differences:

  • Challenge: Bacterial systems lack eukaryotic post-translational modifications

  • Solutions:

    • Express in yeast systems for closer modification patterns

    • Verify activity of non-modified protein

    • Characterize differences between native and recombinant forms

    • Consider chemical modification strategies if necessary

• Protein stability during storage:

  • Challenge: Activity loss during storage

  • Solutions:

    • Add stabilizing agents (glycerol, trehalose)

    • Store at appropriate temperatures (typically -80°C for long-term)

    • Avoid repeated freeze-thaw cycles

    • Consider lyophilization with proper excipients

• Assay interference:

  • Challenge: Buffer components or contaminants affecting enzyme assays

  • Solutions:

    • Perform extensive dialysis before activity assays

    • Include appropriate controls for buffer effects

    • Optimize protein purity (>90% by SDS-PAGE)

    • Consider alternative detection methods if interference persists

When working specifically with Ajellomyces capsulata 3-ketoacyl-CoA reductase, researchers should follow the reconstitution protocol described in section 2.1 and be aware that repeated freeze-thaw cycles are not recommended .

How can researchers optimize experimental conditions to study enzyme behavior in contexts that mimic in vivo environments?

To generate biologically relevant insights, experimental conditions should approximate the physiological environment:

• Physiologically relevant buffer systems:

  • Use buffers that mimic fungal cytoplasmic conditions:

    • pH range: 6.8-7.2

    • Ionic composition reflecting intracellular environment

    • Addition of relevant cofactors (NADPH for 3-ketoacyl-CoA reductase)

  • Consider the impact of crowding agents (PEG, Ficoll) to mimic cellular viscosity

• Temperature and oxygen considerations:

  • Conduct experiments at physiologically relevant temperatures (37°C for mammalian host conditions)

  • Consider microaerophilic conditions that may exist in certain host tissues

  • Assess enzyme behavior under both yeast and hyphal-promoting conditions

• Host-mimicking stress conditions:

  • Incorporate iron limitation using chelators like apo-transferrin (5 μM) as described in

  • Test enzyme function under oxidative stress (H₂O₂ challenge)

  • Assess activity in the presence of host defense molecules

• Advanced ex vivo systems:

  • Use cell extracts rather than purified components to include natural cofactors

  • Develop reconstituted systems with multiple enzymes from related pathways

  • Implement microfluidic systems to control microenvironment parameters

Research on H. capsulatum has demonstrated methods for studying proteins under iron-restricted conditions and within activated macrophages, which could be adapted to investigate 3-ketoacyl-CoA reductase specifically .