Recombinant Nautilia profundicola Elongation factor G (fusA), partial

What is Nautilia profundicola and why is its Elongation Factor G significant for research?

Nautilia profundicola strain Am-H is a moderately thermophilic, deeply-branching Epsilonproteobacterium found in hydrothermal vents and as part of the microbial community on the dorsal surface of vent polychaete, Alvinella pompejana . This organism is particularly significant as a model for studying adaptation to extreme environments that may reflect conditions of early Earth. Its Elongation Factor G (fusA) is of interest because:

• It functions in protein synthesis under extreme temperature and redox fluctuations

• As a housekeeping gene, fusA can provide insights into evolutionary adaptations within the Epsilonproteobacteria

• Understanding its structural adaptations could inform biotechnology applications requiring thermostable translation factors

• The gene can serve as a molecular marker for phylogenetic studies of deep-sea vent microbes

N. profundicola has adapted to survive in anaerobic, sulfur, H₂- and CO₂-rich environments with fluctuating redox potentials and temperatures , making its translation machinery proteins like fusA potentially unique in structure and function.

What expression systems are most effective for producing recombinant N. profundicola fusA protein?

Methodological answer:

The optimal expression system for recombinant N. profundicola fusA depends on your experimental objectives. Based on research with similar proteins from extremophiles, consider these approaches:

For successful expression:

• Optimize codon usage for the host organism

• Consider using a truncated (partial) construct if the full-length protein is difficult to express

• Test multiple fusion tags (His, GST, MBP) to identify optimal solubility

• Implement a stepwise temperature reduction protocol during induction for E. coli systems

• Supplement growth media with rare amino acids and cofactors used by extremophiles

The moderately thermophilic nature of N. profundicola (optimal growth at approximately 40°C) suggests that standard mesophilic expression systems with temperature modification should be sufficient .

How should researchers purify recombinant N. profundicola fusA to maintain its native properties?

The purification strategy should account for the unique properties of N. profundicola proteins adapted to hydrothermal vent conditions:

• Buffer composition:

  • Use buffers containing 5-10% glycerol to improve protein stability

  • Include reducing agents (DTT or β-mercaptoethanol) to maintain proper disulfide bonding

  • Consider including trace amounts of sulfide compounds (0.1-0.5 mM) to mimic natural environment

• Temperature considerations:

  • Perform purification steps at 25-30°C rather than traditional 4°C

  • Test thermal stability during each purification step to monitor activity

• Recommended purification workflow:

  • Initial capture: Immobilized metal affinity chromatography (IMAC) if His-tagged

  • Intermediate purification: Ion exchange chromatography (IEX)

  • Polishing: Size exclusion chromatography (SEC)

  • Quality control: Circular dichroism (CD) to assess secondary structure integrity

• Stability assessment:

  • Monitor activity at various temperatures (30-60°C)

  • Test stability under different redox conditions to ensure native conformation

Remember that N. profundicola has adapted to environments with fluctuating redox potentials , so maintaining appropriate redox conditions during purification is critical for protein function.

How do structural adaptations in N. profundicola fusA compare to those from other extremophiles and mesophiles?

Structural adaptations in N. profundicola fusA likely reflect the unique environmental pressures of deep-sea hydrothermal vents. While specific structural data for N. profundicola fusA is limited, comparative analysis with other extremophiles suggests several probable adaptations:

N. profundicola occupies an interesting intermediate niche as a moderate thermophile (rather than hyperthermophile), suggesting its fusA may have distinctive features. Given that N. profundicola contains the gene (rgy) encoding reverse gyrase , a protein typically associated with hyperthermophiles, its fusA may incorporate some thermophilic adaptations while maintaining flexibility for function across temperature ranges.

To experimentally validate these predictions:

• Perform comparative in silico analysis of fusA sequences across temperature-diverse Epsilonproteobacteria

• Conduct thermal denaturation studies using differential scanning fluorimetry

• Utilize hydrogen-deuterium exchange mass spectrometry to identify flexible regions

What role might N. profundicola fusA play in adaptation to rapid temperature fluctuations in hydrothermal vent environments?

N. profundicola inhabits environments characterized by rapid temperature fluctuations, and its elongation factor G likely plays a critical role in maintaining protein synthesis under these challenging conditions. Research suggests several adaptive mechanisms:

• Temperature-responsive expression regulation:

  • Similar to the observed 100-fold induction of reverse gyrase (rgy) with a 20°C temperature increase , fusA may show temperature-responsive expression patterns

  • Potential temperature-sensitive promoter elements may regulate fusA expression

• Functional adaptation mechanisms:

  • Conditional conformational changes that maintain activity across broader temperature ranges

  • Potential interaction with thermostable ribosomes to preserve translation capabilities

  • Association with molecular chaperones during temperature shifts

• Experimental data from related systems suggests:

To investigate this function experimentally:

• Perform qRT-PCR analysis of fusA expression under different temperature regimes

• Measure in vitro translation rates using purified components at various temperatures

• Analyze ribosome association patterns during temperature shifts

• Compare the temperature adaptation mechanisms with those used for the reverse gyrase protein, which shows dramatic induction with temperature increases

How does N. profundicola fusA function within the context of the organism's unique nitrogen metabolism?

N. profundicola employs a novel nitrate ammonification pathway (reverse-HURM) that differs from classical pathways found in other bacteria . The elongation factor G may have specialized features to facilitate protein synthesis under these unique metabolic conditions:

• Potential specialized roles:

  • Preferential translation of nitrogen metabolism proteins during nitrate utilization

  • Adaptation to pH and ionic changes associated with hydroxylamine and ammonium intermediates

  • Possible moonlighting functions beyond translation, as seen in other extremophiles

• Expression correlation with nitrogen metabolism:

  • While specific fusA expression data is not available, other genes in N. profundicola show strong differential expression under different nitrogen conditions

  • Key genes of the reverse-HURM pathway show 4.6 to 10.3-fold increased expression in nitrate-grown cells compared to ammonium-grown cells

  • It would be valuable to analyze whether fusA expression correlates with these nitrogen metabolism genes

• Experimental approach to investigate this relationship:

  • Perform co-expression analysis of fusA with nitrogen metabolism genes

  • Analyze fusA promoter for nitrogen-responsive elements

  • Test whether recombinant fusA activity is affected by intermediates of the reverse-HURM pathway

What experimental approaches can assess the thermal stability mechanisms of recombinant N. profundicola fusA?

To comprehensively evaluate the thermal stability mechanisms of recombinant N. profundicola fusA, employ these methodological approaches:

Based on N. profundicola's adaptation to environments with fluctuating temperatures , its fusA likely employs multiple stabilization strategies rather than a single mechanism, making a multi-technique approach essential.

How might post-translational modifications of N. profundicola fusA differ from those in mesophilic bacteria?

Post-translational modifications (PTMs) may play a crucial role in N. profundicola fusA function and adaptation to extreme conditions. While direct evidence for N. profundicola fusA PTMs is limited, comparative analysis suggests several possibilities:

• Predicted PTM differences:

• Environmental influences on PTMs:

  • Sulfur-rich environment of hydrothermal vents may favor sulfur-containing modifications

  • Fluctuating redox conditions may necessitate reversible redox-sensitive modifications

  • Temperature variations could require temperature-responsive modifications

• Methodological approach to identify PTMs:

  • Mass spectrometry analysis of purified recombinant and native fusA

  • Comparison of modification patterns under different growth conditions

  • Functional assessment of proteins with and without specific modifications

• PTM machinery analysis:

  • Examine N. profundicola genome for presence of modification enzymes

  • Compare with those found in related Epsilonproteobacteria

  • Identify unique modification pathways

The numerous stress response systems identified in the N. profundicola genome suggest sophisticated regulation mechanisms that likely extend to translational machinery proteins like fusA.

What control experiments are essential when working with recombinant N. profundicola fusA?

When designing experiments with recombinant N. profundicola fusA, implement these essential controls:

• Protein quality controls:

  • SDS-PAGE analysis for purity assessment (>95% purity recommended)

  • Western blot confirmation of identity using anti-His tag and anti-fusA antibodies

  • Mass spectrometry verification of intact mass and peptide mapping

  • Circular dichroism to confirm proper secondary structure formation

• Activity controls:

  • Parallel testing of E. coli fusA as a mesophilic reference

  • Temperature-dependent activity profiling (20-70°C)

  • GTPase activity measurement under standard conditions

  • Ribosome binding and translation activity assays

• Stability controls:

  • Time-course stability at storage and experimental temperatures

  • Freeze-thaw stability assessment

  • Buffer composition effects on activity maintenance

  • Redox stability with various reducing agents

• Experimental design controls:

  • Validate each new protein preparation against previous batches

  • Run parallel experiments with heat-inactivated protein

  • Include buffer-only controls for all assays

  • Test for interfering factors from the expression system

• Environmental condition controls:

  • Test activity across pH ranges relevant to hydrothermal vents (pH 5.5-8.0)

  • Evaluate effects of various metal ions at concentrations found in vent environments

  • Assess impact of sulfur compounds found in N. profundicola's natural habitat

These controls are particularly important given N. profundicola's adaptation to extreme and fluctuating environmental conditions , which may result in unique protein behavior compared to mesophilic model systems.

How can researchers optimize heterologous expression of N. profundicola fusA for structural studies?

Optimizing heterologous expression of N. profundicola fusA for structural studies requires addressing several challenges specific to proteins from extremophiles:

• Expression construct optimization:

  • Test both full-length and truncated constructs based on domain predictions

  • Employ fusion partners known to enhance solubility (MBP, SUMO, or TrxA)

  • Design constructs with precision-cleavable tags for crystallography

  • Consider codon optimization for expression host

• Expression conditions matrix:

• Purification strategy for structural studies:

  • Implement two orthogonal chromatography steps minimum

  • Screen multiple buffers using thermal shift assays (TSA)

  • Include GTP or non-hydrolyzable analogs to stabilize conformation

  • Assess homogeneity by dynamic light scattering (DLS)

• Protein quality verification for structural studies:

  • Size-exclusion chromatography with multi-angle light scattering (SEC-MALS)

  • Mass photometry for oligomeric state determination

  • Limited proteolysis to identify stable domains

  • Initial crystallization screening at multiple concentrations

• Alternative expression systems if E. coli fails:

  • Cell-free expression systems

  • Bacillus subtilis for gram-positive expression

  • Methylotrophic yeasts for eukaryotic expression with prokaryotic codon preference

Given that N. profundicola contains all the genes necessary for life in extreme anaerobic, sulfur, H₂- and CO₂-rich environments with fluctuating redox potentials and temperatures , its proteins may require special consideration for optimal expression and stability.

What bioinformatic approaches can identify unique features of N. profundicola fusA compared to mesophilic homologs?

Conducting comprehensive bioinformatic analysis of N. profundicola fusA requires multi-faceted approaches:

• Sequence-based comparisons:

  • Multiple sequence alignment with fusA from diverse thermal environments

  • Calculate amino acid composition bias (e.g., increased Glu, Asp, Arg, Lys in thermophiles)

  • Identify conserved domains and unique insertions/deletions

  • Analyze codon usage patterns and GC content in the gene sequence

• Structural prediction and analysis:

  • Generate homology models based on available crystal structures

  • Calculate electrostatic surface potentials

  • Identify potential ionic interaction networks

  • Analyze predicted flexibility using normal mode analysis

• Evolutionary analysis:

  • Construct phylogenetic trees using maximum likelihood methods

  • Calculate selection pressures (dN/dS) across different domains

  • Identify potential horizontal gene transfer events

  • Trace evolutionary patterns within Epsilonproteobacteria

• Specialized feature analysis:

• Integration with genomic context:

  • Analyze genomic neighborhood of fusA

  • Compare with synteny in related species

  • Identify potential co-regulated genes

  • Examine promoter regions for unique regulatory elements

These approaches can reveal how N. profundicola fusA has adapted to function in extreme deep-sea hydrothermal vent environments characterized by fluctuating temperatures and redox states .

How can researchers accurately interpret kinetic data from N. profundicola fusA considering its environmental adaptations?

Interpreting kinetic data from N. profundicola fusA requires special considerations due to its adaptation to extreme and fluctuating conditions:

• Temperature-dependence considerations:

  • Construct full temperature-activity profiles (20-70°C)

  • Calculate activation energy (Ea) using Arrhenius plots

  • Determine temperature optimum and compare to organism's growth temperature

  • Evaluate temperature effects on substrate affinity (Km) separately from catalytic rate (kcat)

• Key parameters to measure across conditions:

• Environmental condition matrix:

  • Test activity across relevant pH range (pH 5.5-8.0)

  • Evaluate effects of salt concentration (0.1-0.5 M NaCl)

  • Assess impact of reducing agents (mimicking redox fluctuations)

  • Measure effects of pressure relevant to deep-sea environments

• Data normalization approaches:

  • Normalize to optimal conditions rather than standard conditions

  • Consider relative activity across environmental variables

  • Compare temperature quotient (Q10) values with mesophilic homologs

  • Develop 3D activity landscapes across multiple variables

• Methodological controls for accurate interpretation:

  • Verify protein stability throughout assay period

  • Account for temperature effects on assay components

  • Implement parallel assays with mesophilic and thermophilic controls

  • Validate results using orthogonal activity measurement techniques

Given that N. profundicola thrives in environments with fluctuating temperatures and redox potentials , its fusA likely exhibits unique kinetic properties adapted to function across varying conditions rather than being optimized for a single condition.

How might N. profundicola fusA be used as a model for studying translational adaptation to extreme environments?

N. profundicola fusA represents an excellent model for investigating translational adaptations to extreme environments for several compelling reasons:

• Evolutionary significance:

  • N. profundicola belongs to the deepest branching lineage of Epsilonproteobacteria

  • Its proteins may retain features reflecting ancient adaptation strategies

  • Comparative studies across thermal adaptation gradients can reveal evolutionary mechanisms

  • May provide insights into the evolution of translation systems under primitive Earth conditions

• Research framework for translational adaptation studies:

• Experimental approaches:

  • Develop reconstituted translation systems with components from N. profundicola

  • Create chimeric translation machinery with components from different thermal environments

  • Implement directed evolution experiments under fluctuating conditions

  • Perform comparative ribosome profiling across environmental conditions

• Broader implications:

  • Insights into adaptation mechanisms relevant to other extremophiles

  • Understanding of protein synthesis under fluctuating conditions in mesophilic pathogens

  • Principles for engineering robust translation systems for biotechnology

  • Models for predicting climate change impacts on microbial protein synthesis

The fact that N. profundicola contains genes for life in conditions that may reflect the early Earth biosphere makes its translational machinery particularly valuable for understanding fundamental adaptation principles.

What emerging techniques could advance the structural characterization of challenging proteins like N. profundicola fusA?

Several cutting-edge techniques show particular promise for characterizing structurally challenging proteins like N. profundicola fusA:

• Cryo-electron microscopy (cryo-EM) advances:

  • Single-particle analysis for high-resolution structure determination without crystallization

  • Time-resolved cryo-EM to capture different conformational states

  • Advantages for dynamic proteins that resist crystallization

  • Particularly valuable for visualizing fusA-ribosome interactions

• Integrated structural biology approaches:

• Dynamic and functional characterization:

  • Single-molecule FRET to track conformational changes in real-time

  • Optical tweezers to measure force generation during translocation

  • Native mass spectrometry to identify binding partners and conformational states

  • High-pressure X-ray crystallography to mimic deep-sea conditions

• In situ structural studies:

  • Cryo-electron tomography of cells expressing tagged fusA

  • Correlative light and electron microscopy to track fusA in cells

  • In-cell NMR to study structure in cellular environment

  • Mass photometry for stoichiometry determination in near-native conditions

• Artificial intelligence integration:

  • Machine learning for improved model building from low-resolution data

  • Neural networks to predict functional consequences of structural features

  • Automated experimental design optimization for challenging proteins

These advanced techniques are particularly valuable for proteins like N. profundicola fusA that may have evolved unique structural adaptations to function under the extreme conditions of hydrothermal vents with fluctuating temperatures and redox states .