Recombinant Salmo salar Probable methylthioribulose-1-phosphate dehydratase (apip)

What is the biological function of methylthioribulose-1-phosphate dehydratase in Salmo salar?

Methylthioribulose-1-phosphate (MTRu-1-P) dehydratase likely plays a critical role in the methionine salvage pathway in Atlantic salmon, similar to its function in other organisms. Based on characterized homologs, this enzyme catalyzes the conversion of MTRu-1-P to 2,3-diketo-5-methylthiopentyl-1-phosphate (DK-MTP-1-P) . The methionine salvage pathway enables recycling of sulfur-containing metabolites, which is particularly important in organisms that must conserve essential amino acids. While this enzyme has been characterized in bacterial systems like Bacillus subtilis, its specific properties in Atlantic salmon require further investigation, though the genomic annotation confirms its presence in this species .

How is the probable MTRu-1-P dehydratase gene structured and annotated in the Salmo salar genome?

The gene encoding probable methylthioribulose-1-phosphate dehydratase in Salmo salar is identified in genomic databases with the following characteristics:

The gene is computationally predicted and annotated based on evidence from EST (Expressed Sequence Tag) data, using the Gnomon gene prediction method .

What are the biochemical properties of MTRu-1-P dehydratase based on characterized homologs?

While the specific biochemical properties of Salmo salar MTRu-1-P dehydratase remain to be fully characterized, insights can be gained from the well-studied Bacillus subtilis enzyme:

When studying the salmon enzyme, these parameters provide starting points for experimental design, though species-specific variations should be anticipated .

What expression systems are most suitable for recombinant production of Salmo salar MTRu-1-P dehydratase?

For recombinant expression of Salmo salar MTRu-1-P dehydratase, several methodological approaches can be considered:

• Vector Selection: The coding sequence can be cloned into expression vectors such as pcDNA3.1+/C-(K)DYK or customized vectors. CloneEZ™ Seamless cloning technology is a viable approach for construct generation .

• Expression Systems:

  • Bacterial Expression: E. coli BL21(DE3) or Rosetta strains are suitable for initial expression attempts, with growth at lower temperatures (16-20°C) to enhance proper folding.

  • Eukaryotic Expression: For more authentic post-translational modifications, consider insect cell systems (Sf9, High Five) or mammalian cell lines (HEK293, CHO).

• Expression Optimization:

  • Codon optimization for the expression host

  • Induction conditions: IPTG concentration (0.1-1.0 mM), temperature (16-37°C), and duration (4-24 hours)

  • Co-expression with chaperones may improve folding and solubility

• Tags and Fusion Partners:

  • N- or C-terminal His6-tag for IMAC purification

  • Fusion partners (MBP, GST, SUMO) to enhance solubility

  • Inclusion of TEV protease cleavage sites for tag removal

Given that the B. subtilis enzyme forms a tetramer, special attention should be paid to conditions that promote proper oligomerization of the salmon enzyme .

What purification strategies are effective for isolating recombinant Salmo salar MTRu-1-P dehydratase?

An effective purification strategy for recombinant Salmo salar MTRu-1-P dehydratase would typically involve:

• Cell Lysis:

  • Buffer composition: 50 mM Tris-HCl (pH 8.0), 300 mM NaCl, 10% glycerol, 1 mM DTT, protease inhibitors

  • Methods: Sonication or high-pressure homogenization for bacterial cells; gentle lysis buffers for eukaryotic cells

• Initial Capture:

  • Affinity chromatography: Ni-NTA for His-tagged proteins or appropriate affinity resins for other tags

  • Binding conditions: 50 mM Tris-HCl (pH 8.0), 300 mM NaCl, 10 mM imidazole

  • Elution: Imidazole gradient (50-300 mM)

• Intermediate Purification:

  • Ion exchange chromatography: Based on theoretical pI of the enzyme

  • Tag cleavage: If necessary, using TEV protease followed by reverse affinity chromatography

• Polishing:

  • Size exclusion chromatography: To separate tetrameric forms from aggregates or monomers

  • Buffer exchange to stabilization buffer: 50 mM HEPES (pH 7.5-8.0), 150 mM NaCl, 10% glycerol, 1 mM DTT

• Quality Control:

  • SDS-PAGE and Western blotting

  • Activity assays

  • Mass spectrometry for identity confirmation

  • Dynamic light scattering for oligomeric state assessment

Throughout purification, maintaining a pH range of 7.5-8.5 is advisable based on the optimal pH range observed for the B. subtilis enzyme .

How can researchers develop reliable activity assays for MTRu-1-P dehydratase?

Developing reliable activity assays for MTRu-1-P dehydratase presents specific challenges, particularly due to the instability of the reaction product. Methodological approaches include:

• Direct Assays:

  • Spectrophotometric monitoring: If the substrate and product have different absorption spectra

  • HPLC analysis with rapid sampling to detect the product before significant decomposition

  • Mass spectrometry to track substrate conversion and product formation

• Coupled Enzyme Assays:

  • Coupling with downstream enzymes in the methionine salvage pathway

  • Designing synthetic coupling systems that generate measurable signals upon DK-MTP-1-P formation

• Substrate Preparation:

  • Chemical synthesis of MTRu-1-P

  • Enzymatic generation using upstream enzymes in the pathway

• Assay Conditions:

  • Buffer: 50 mM HEPES or Tris-HCl (pH 7.5-8.5)

  • Temperature range: 25-40°C (with 40°C likely optimal based on B. subtilis enzyme)

  • Substrate concentration: Starting with 5-10× Km (approximately 50-100 μM based on B. subtilis enzyme)

• Addressing Product Instability:

  • Rapid quenching and analysis

  • Temperature adjustment to slow decomposition

  • Mathematical correction for decomposition using the established rate constant (k = 0.048 s⁻¹ in B. subtilis)

How does expression of MTRu-1-P dehydratase vary across different tissues and developmental stages in Salmo salar?

While the search results don't provide direct data on tissue-specific or developmental expression patterns of MTRu-1-P dehydratase in Salmo salar, a methodological approach to investigating this question would include:

• Tissue-Specific Expression Analysis:

  • Quantitative RT-PCR targeting the LOC106587892 transcript across tissues (gill, liver, muscle, brain, kidney, intestine, etc.)

  • RNA-seq analysis of tissue-specific transcriptomes

  • In situ hybridization to localize expression within tissues

• Developmental Profiling:

  • Time-course sampling from embryonic stages through adult development

  • Stage-specific quantitative expression analysis

  • Correlation with developmental milestones and environmental transitions (freshwater to seawater)

• Protein-Level Confirmation:

  • Western blotting with specific antibodies

  • Proteomics approaches for unbiased detection

  • Enzyme activity assays in tissue extracts

• Regulatory Analysis:

  • Promoter characterization and identification of transcription factor binding sites

  • Epigenetic profiling to identify potential regulatory mechanisms

This systematic approach would establish the spatiotemporal expression pattern of MTRu-1-P dehydratase and provide insights into its physiological roles in different salmon tissues and life stages.

How does MTRu-1-P dehydratase expression respond to pathogen challenges in Atlantic salmon?

Based on transcriptomic studies of Atlantic salmon responses to infections, methodological approaches to investigate MTRu-1-P dehydratase regulation during pathogen challenges include:

• Controlled Infection Studies:

  • Challenge models with relevant pathogens (sea lice, ISAv, bacterial pathogens)

  • Time-course sampling post-infection

  • Combined challenges to model co-infection scenarios

• Transcriptomic Analysis:

  • RNA-seq analysis of infected vs. uninfected tissues

  • Differential expression analysis of LOC106587892 (MTRu-1-P dehydratase) transcript

  • Pathway enrichment analysis to contextualize expression changes

• Validation and Functional Studies:

  • qRT-PCR confirmation of expression changes

  • Correlation with immune markers and pathway activation

  • In vitro models using salmon cell lines challenged with pathogen-associated molecular patterns

While specific data on MTRu-1-P dehydratase regulation during infection isn't provided in the search results, the existing experimental framework for salmon transcriptomics during sea lice and ISAv infection provides a valuable model . These infections trigger complex transcriptomic responses, including modulation of metabolic pathways, which might include methionine metabolism.

How do nutritional factors influence MTRu-1-P dehydratase expression and activity in Salmo salar?

Investigating nutritional regulation of MTRu-1-P dehydratase in Atlantic salmon can build upon existing experimental approaches for studying diet-dependent gene expression:

• Experimental Diet Formulations:

  • Varying levels of methionine and other sulfur amino acids

  • Different lipid compositions (as shown in existing studies with varying EPA/DHA and ω-3/ω-6 ratios)

  • Inclusion of immunostimulants and functional feed additives

• Feeding Trials:

  • Controlled feeding experiments with different diet formulations

  • Sampling schedule to capture acute and chronic responses

  • Tissue collection focused on metabolically active organs (liver, intestine)

• Analytical Approaches:

  • Transcriptomic analysis (RNA-seq, qRT-PCR) targeting MTRu-1-P dehydratase

  • Enzyme activity assays in tissue extracts

  • Metabolomic analysis of methionine pathway intermediates

• Integration with Challenge Models:

  • Combining nutritional interventions with pathogen challenges

  • Evaluating the interaction between diet and stress responses

Based on existing salmon nutrition studies that examined four experimental diets (varying in EPA/DHA content, ω-3/ω-6 ratios, and immunostimulants), similar approaches could be applied to investigate how these dietary factors specifically influence methionine metabolism and MTRu-1-P dehydratase expression .

How conserved is MTRu-1-P dehydratase across fish species and other vertebrates?

A comprehensive approach to analyzing the evolutionary conservation of MTRu-1-P dehydratase would involve:

• Sequence Analysis:

  • Multiple sequence alignment of MTRu-1-P dehydratase proteins from diverse species

  • Identification of conserved domains, catalytic residues, and structural motifs

  • Phylogenetic tree construction to visualize evolutionary relationships

• Structural Comparisons:

  • Homology modeling of fish MTRu-1-P dehydratases based on available crystal structures

  • Structural superposition to identify conserved catalytic geometry

  • Analysis of species-specific structural adaptations

• Functional Conservation Assessment:

  • Comparative biochemical characterization across species

  • Complementation studies in model organisms

  • Analysis of expression patterns in different vertebrate lineages

• Genomic Context Analysis:

  • Synteny analysis to examine conservation of genomic neighborhoods

  • Analysis of gene duplication events in different lineages

  • Identification of lineage-specific regulatory elements

The "methylthioribulose-1-phosphate dehydratase-like" annotation in Salmo salar suggests sequence similarity to characterized enzymes in other organisms , indicating conservation of this metabolic function across species.

What structural features distinguish fish MTRu-1-P dehydratase from bacterial homologs?

While detailed structural information specific to the salmon enzyme is not provided in the search results, a methodological approach to this question would include:

• Primary Sequence Analysis:

  • Comparison of amino acid composition and sequence motifs

  • Identification of fish-specific insertions or deletions

  • Analysis of potential post-translational modification sites present in eukaryotic but not bacterial enzymes

• Structural Prediction and Modeling:

  • Homology modeling using bacterial crystal structures as templates

  • Analysis of predicted quaternary structure (tetramer formation)

  • Molecular dynamics simulations to evaluate structural stability

• Functional Domain Analysis:

  • Comparison of catalytic domains

  • Analysis of potential regulatory domains present in fish but not bacterial enzymes

  • Evaluation of substrate binding pocket architecture

• Experimental Validation:

  • Site-directed mutagenesis of predicted key residues

  • Chimeric protein construction to identify functional domains

  • Crystallization attempts for direct structural determination

From the bacterial enzyme characterization, we know that B. subtilis MTRu-1-P dehydratase functions as a tetramer with specific biochemical properties . The salmon enzyme, being a eukaryotic protein, may have additional regulatory features or structural adaptations suited to the cellular environment of fish.

How can MTRu-1-P dehydratase be used as a model to study evolutionary adaptation of metabolic pathways in fish?

MTRu-1-P dehydratase provides an excellent model system for studying metabolic pathway evolution in fish, with several methodological approaches:

• Comparative Genomics Framework:

  • Analysis of gene copy number across fish species with different environmental adaptations

  • Identification of selection signatures in coding regions

  • Correlation of sequence variations with habitat and dietary preferences

• Biochemical Adaptation Studies:

  • Characterization of enzyme kinetics across fish species from different thermal environments

  • Comparison of substrate specificity and catalytic efficiency

  • Analysis of enzyme stability under various physiological conditions

• Expression Pattern Analysis:

  • Comparison of tissue-specific expression across species

  • Analysis of regulatory mechanisms in different lineages

  • Correlation with metabolic requirements in different ecological niches

• Functional Genomics Approaches:

  • CRISPR/Cas9-mediated gene editing to study functional consequences of variations

  • Heterologous expression studies to assess functional equivalence

  • Metabolic flux analysis to quantify pathway differences

This enzyme's role in the methionine salvage pathway makes it particularly interesting for studying how core metabolic functions adapt to different environmental pressures while maintaining essential functionality.

How might MTRu-1-P dehydratase function be integrated into broader metabolic networks during salmon immune responses?

Integration of MTRu-1-P dehydratase function into immune response networks could be investigated through:

• Systems Biology Approaches:

  • Network analysis of transcriptomic data from infection studies

  • Identification of co-regulated gene clusters including MTRu-1-P dehydratase

  • Pathway enrichment analysis to identify connections to immune functions

• Metabolic Flux Analysis:

  • Stable isotope tracing of methionine metabolism during immune activation

  • Quantification of pathway activity changes during infection

  • Integration with immunometabolic models

• Functional Interventions:

  • Gene knockdown studies to assess the impact on immune responses

  • Metabolic inhibitor studies targeting the methionine salvage pathway

  • Nutritional supplementation studies with pathway precursors

Based on transcriptomic studies of salmon during pathogen challenges, immune responses involve complex metabolic reprogramming . The methionine salvage pathway might be integrated with immune functions through:

• Provision of methionine for acute phase protein synthesis

• Regulation of methylation reactions important for immune signaling

• Connections to polyamine metabolism, which influences cell proliferation during immune responses

What are the potential impacts of climate change factors on MTRu-1-P dehydratase function in Atlantic salmon?

Investigating the effects of climate change factors on MTRu-1-P dehydratase function requires multifaceted approaches:

Climate change factors could affect enzyme function through direct effects on protein stability and catalytic efficiency, as well as through broader impacts on gene expression regulation and metabolic network reorganization in response to environmental stress.