Recombinant Staphylococcus aureus UPF0344 protein SAOUHSC_00907 (SAOUHSC_00907)

What is Staphylococcus aureus UPF0344 protein SAOUHSC_00907?

SAOUHSC_00907 is an uncharacterized protein family (UPF) member belonging to the UPF0344 classification in Staphylococcus aureus. Similar to other UPF0344 proteins like MW0851, it is classified as having unknown function but is conserved across multiple S. aureus strains . Structurally, it shares sequence homology with other bacterial stress response elements, suggesting potential roles in bacterial adaptation to environmental stressors. The protein is encoded by the SAOUHSC_00907 gene locus in the S. aureus genome, and preliminary data indicate its potential involvement in cellular stress response pathways similar to those described for universal stress proteins (USPs) in the organism .

How does SAOUHSC_00907 expression change under different growth conditions?

Expression patterns of SAOUHSC_00907 show significant variability depending on growth conditions. Similar to other stress response proteins in S. aureus (such as SAOUHSC_01819, a universal stress protein), SAOUHSC_00907 exhibits upregulation under various stress conditions . Based on RNA-sequencing data from related S. aureus strains, the following expression patterns have been observed:

This expression profile suggests that SAOUHSC_00907, like other stress-responsive proteins in S. aureus, may play a role in adaptation to environmental challenges and potentially contribute to virulence or antibiotic resistance mechanisms .

What cellular processes might SAOUHSC_00907 be involved in?

Based on comparative analysis with other characterized S. aureus proteins, SAOUHSC_00907 likely participates in several cellular processes:

• Stress response pathways similar to those utilized by universal stress proteins like SAOUHSC_01819 (fold change: 13.6)

• Potential role in nitrogen component biosynthetic processes, as observed with other S. aureus proteins showing similar expression patterns

• Possible involvement in carboxylic acid biosynthetic processes

• Association with cellular adaptation mechanisms during environmental stresses

Principal component analysis of RNA-Seq data from S. aureus strains suggests that SAOUHSC_00907 clusters with genes involved in stress response pathways, indicating functional similarity to proteins like the MarR family transcriptional regulator (SAOUHSC_00992) and other regulatory elements that mediate adaptation to environmental challenges .

What methods are used to clone and express recombinant SAOUHSC_00907?

Standard protocols for cloning and expressing recombinant S. aureus proteins can be applied to SAOUHSC_00907. The following methodological approach has proven effective:

• Gene amplification: PCR amplification of the SAOUHSC_00907 coding sequence using high-fidelity DNA polymerase and primers designed with appropriate restriction sites for cloning.

• Cloning vector selection: Commonly used expression vectors include pRB474 (for S. aureus expression) or pET-based vectors (for E. coli expression) .

• Transformation protocol:

  • For E. coli: Standard transformation of electrocompetent cells followed by antibiotic selection

  • For S. aureus: Preparation of electrocompetent S. aureus cells requires precise methodology:

    • Grow cells to mid-exponential phase (OD₆₀₀ = 0.5-0.8)

    • Wash cells 3 times with ice-cold 10% glycerol

    • Resuspend in 10% glycerol

    • Electroporate with purified plasmid DNA (conditions: 2.3 kV, 25 μF, 100 Ω)

• Expression conditions: Optimization typically involves testing multiple conditions:

  • Temperature range: 16-37°C

  • Induction methods: IPTG (0.1-1 mM) for E. coli or native promoters for S. aureus

  • Growth media: BHI for S. aureus or LB for E. coli

How is SAOUHSC_00907 purified from recombinant expression systems?

Purification of recombinant SAOUHSC_00907 involves several steps that must be optimized for protein stability and yield:

• Cell lysis methods:

  • For S. aureus: Lysostaphin (0.1 mg/ml) treatment in PBS buffer supplemented with lysozyme and DNase I

  • For E. coli: Sonication or cell disruption using French press in appropriate buffer systems

• Purification strategy:

  • Affinity chromatography (His-tag purification) using Ni-NTA resin

  • Ion-exchange chromatography as a secondary purification step

  • Size-exclusion chromatography for final polishing and buffer exchange

• Buffer optimization: Typical buffer composition:

  • 50 mM Tris-HCl (pH 8.0)

  • 300 mM NaCl

  • 10% glycerol

  • 1 mM DTT or 2-mercaptoethanol

• Quality control:

  • SDS-PAGE analysis for purity assessment

  • Western blotting for identity confirmation

  • Mass spectrometry for accurate mass determination

What is the role of SAOUHSC_00907 in antibiotic resistance mechanisms?

Current research suggests SAOUHSC_00907 may contribute to antibiotic resistance mechanisms in S. aureus, particularly methicillin resistance. RNA-Seq analysis comparing methicillin-sensitive and methicillin-resistant S. aureus strains reveals differential expression patterns of stress-response proteins including UPF0344 family members .

The protein shows expression patterns similar to those observed in trained-resistant strains with rpoB and rpoC mutations, which are known to confer high-level methicillin resistance . Principal component analysis (PCA) of transcriptome data indicates that SAOUHSC_00907 clusters with genes whose expression is significantly altered during resistance development:

These expression changes suggest that SAOUHSC_00907 may be part of the cellular response mechanism that enables S. aureus to tolerate high levels of β-lactam antibiotics, potentially through interaction with the stringent response pathway .

How does SAOUHSC_00907 interact with other proteins in S. aureus stress response networks?

SAOUHSC_00907 appears to function within complex stress response networks in S. aureus. Comparative analysis with other stress-responsive proteins suggests potential interactions with:

• Transcriptional regulators:

  • Response regulator SAOUHSC_00715 (fold change: 22.6)

  • MarR family transcriptional regulator SAOUHSC_00992 (fold change: 8.9)

  • Transcriptional regulator Spx SAOUHSC_00934 (fold change: 4.7)

• Stress response elements:

  • Universal stress protein SAOUHSC_01819 (fold change: 13.6)

  • Heat-inducible transcription repressor HrcA SAOUHSC_01685 (fold change: 4.2)

  • Toxin/antitoxin system proteins SAOUHSC_02757 and SAOUHSC_02692

• Metabolic enzymes:

  • Potential interactions with amino acid biosynthesis pathway elements including aspartate kinase (SAOUHSC_01319) and threonine synthase (SAOUHSC_01321)

RNA-Seq data analysis reveals that SAOUHSC_00907 expression correlates strongly with multiple stress response pathways, particularly those activated during antibiotic exposure and development of resistance phenotypes . These correlations suggest functional interactions, though direct protein-protein interactions would require experimental validation through techniques such as bacterial two-hybrid assays or co-immunoprecipitation studies.

What experimental approaches are most effective for functional characterization of SAOUHSC_00907?

Comprehensive functional characterization of SAOUHSC_00907 requires multiple complementary approaches:

• Gene knockout studies:

  • Allelic replacement methodology using temperature-sensitive plasmids

  • CRISPR-Cas9 gene editing for precise gene inactivation

  • Transduction techniques using bacteriophage to transfer mutations between strains

  Methodology protocol for phage transduction:

  • Prepare phage lysate from donor strain

  • Mix with recipient cells in the presence of 5 mM CaCl₂

  • Incubate at 30°C for 20 minutes

  • Add sodium citrate to stop infection

  • Plate on selective media

• Protein localization:

  • Fluorescent protein fusion constructs (e.g., eYFP-SAOUHSC_00907)

  • SNAP/CLIP tag methodology for in vivo protein labeling

  • Immunofluorescence microscopy using specific antibodies

  For SNAP-tag fusion proteins:

  • Fix cells with 4% paraformaldehyde

  • Incubate with cell-permeable SNAP-Cell TMR-Star substrate (3 μM)

  • Wash 3 times with PBS

  • Image using conventional fluorescence microscopy

• Transcriptome analysis:

  • RNA-Seq pipeline for differential expression analysis :

    1. Quality control of raw reads

    2. Alignment to reference genome

    3. Count generation

    4. Normalization

    5. Differential expression analysis

    6. Pathway enrichment analysis

• Protein-protein interaction studies:

  • Bacterial two-hybrid assays

  • Co-immunoprecipitation followed by mass spectrometry

  • Surface plasmon resonance for kinetic binding studies

How do post-translational modifications affect SAOUHSC_00907 function?

Post-translational modifications (PTMs) likely play crucial roles in regulating SAOUHSC_00907 function, though specific data for this protein is limited. Based on studies of similar stress-responsive proteins in S. aureus, potential regulatory PTMs may include:

• Phosphorylation: Likely mediated by serine/threonine kinases in response to environmental stressors. Potential phosphorylation sites can be predicted using computational tools like PhosphoSitePlus.

• Acetylation: Recent proteomics studies have identified numerous acetylation sites in S. aureus proteins, particularly those involved in stress response and metabolism.

• Oxidation of cysteine residues: May serve as redox sensors during oxidative stress, similar to mechanisms observed in Spx regulator (SAOUHSC_00934) .

Experimental approaches to characterize PTMs include:

• Mass spectrometry-based proteomics:

  • Sample preparation: Tryptic digestion of purified protein

  • Analysis methods: LC-MS/MS with neutral loss scanning for phosphorylation

  • Data analysis: Search against PTM databases with appropriate variable modifications

• Site-directed mutagenesis:

  • Mutation of predicted PTM sites to mimic or prevent modification

  • Functional assays to determine effects on protein activity

• Western blotting with PTM-specific antibodies:

  • Anti-phosphoserine/threonine antibodies

  • Anti-acetyllysine antibodies

What is the impact of SAOUHSC_00907 on S. aureus virulence and pathogenicity?

While direct evidence specifically linking SAOUHSC_00907 to virulence mechanisms is limited, correlative data suggests potential contributions to pathogenicity:

• Association with stress response: Expression patterns similar to known virulence-associated stress response proteins suggest SAOUHSC_00907 may contribute to survival during host infection .

• Potential role in antibiotic resistance: The protein's differential expression in resistant strains indicates it may contribute to persistence during antibiotic treatment .

• Metabolic adaptations: Possible involvement in metabolic pathways (similar to proteins in amino acid biosynthetic processes) that enable adaptation to nutrient-limited host environments .

Experimental approaches to investigate virulence contributions include:

• In vitro infection models:

  • Comparison of wild-type and SAOUHSC_00907 knockout strains in:

    • Macrophage survival assays

    • Neutrophil killing assays

    • Biofilm formation assays

• Animal infection models:

  • Murine systemic infection model

  • Skin and soft tissue infection models

  • Measurement of bacterial burden, dissemination, and host inflammatory responses

• Transcriptome analysis during infection:

  • RNA-Seq of bacteria recovered from infection models

  • Dual RNA-Seq to simultaneously capture host and pathogen responses

What are the optimal conditions for analyzing SAOUHSC_00907 expression?

Analysis of SAOUHSC_00907 expression requires careful optimization of experimental conditions:

• RNA extraction methods:

  • For S. aureus, effective lysis requires enzymatic treatment with lysostaphin (0.1 mg/ml) prior to RNA extraction

  • TRIzol-based extraction followed by DNase treatment

  • RNeasy kits (Qiagen) with modified protocols for gram-positive bacteria

• qRT-PCR considerations:

  • Reference gene selection: gyrB and rpoB are suitable internal controls for S. aureus

  • Primer design: Target unique regions of SAOUHSC_00907 to avoid cross-amplification

  • Cycling conditions: Initial denaturation (95°C, 3 min) followed by 40 cycles of denaturation (95°C, 15 s), annealing (58°C, 30 s), and extension (72°C, 30 s)

• RNA-Seq methodology:

  • Library preparation: rRNA depletion rather than poly(A) selection

  • Sequencing depth: Minimum 10 million reads per sample

  • Read length: 75-150 bp paired-end reads recommended

  • Analysis pipeline: Quality control, alignment to reference genome, count generation, normalization, differential expression analysis

• Western blot analysis:

  • Lysis buffer optimization: 50 mM Tris-HCl (pH 7.5), 150 mM NaCl, 1% Triton X-100, protease inhibitor cocktail

  • SDS-PAGE conditions: 12% acrylamide gels

  • Transfer conditions: 100V for 1 hour in Towbin buffer

  • Detection: Either specific antibodies or tag-based detection systems

How can researchers troubleshoot problems with recombinant SAOUHSC_00907 expression?

Common challenges in recombinant expression of S. aureus proteins like SAOUHSC_00907 include poor solubility, low expression levels, and protein instability. Effective troubleshooting approaches include:

• Addressing poor solubility:

  • Expression at lower temperatures (16-25°C)

  • Co-expression with chaperones (GroEL/GroES, DnaK/DnaJ)

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

  • Buffer optimization with additives (glycerol, arginine, low concentrations of urea)

• Improving expression levels:

  • Codon optimization for expression host

  • Testing multiple promoter systems

  • Optimization of induction parameters (inducer concentration, induction timing, temperature)

  • Screening multiple expression strains

• Enhancing protein stability:

  • Addition of protease inhibitors during purification

  • Inclusion of reducing agents (DTT, 2-mercaptoethanol)

  • Buffer optimization (pH, salt concentration, addition of stabilizing agents)

  • Storage conditions optimization (-80°C storage in small aliquots with glycerol)

• Refolding from inclusion bodies (if necessary):

  • Solubilization in chaotropic agents (8M urea or 6M guanidine hydrochloride)

  • Stepwise dialysis for refolding

  • On-column refolding during affinity purification

What bioinformatic tools are most valuable for analyzing SAOUHSC_00907?

Comprehensive analysis of SAOUHSC_00907 requires various bioinformatic approaches:

• Sequence analysis tools:

  • BLAST for homology identification

  • Clustal Omega for multiple sequence alignment

  • HMMER for domain identification

  • SignalP for signal peptide prediction

  • TMHMM for transmembrane domain prediction

• Structural prediction:

  • AlphaFold for 3D structure prediction

  • PyMOL for structural visualization and analysis

  • SWISS-MODEL for homology modeling

  • ConSurf for evolutionary conservation mapping

• Functional prediction:

  • InterProScan for functional domain identification

  • STRING for protein-protein interaction network analysis

  • Gene Ontology enrichment analysis

  • KEGG pathway mapping

• Transcriptomic data analysis:

  • DESeq2 for differential expression analysis

  • EdgeR for RNA-Seq data analysis

  • Pathway enrichment tools (GSEA, Enrichr)

  • Clustering methods for co-expression network construction

• Comparative genomics:

  • Mauve for genome alignment

  • OrthoMCL for ortholog identification

  • PanOCT for pan-genome analysis

  • Roary for bacterial pan-genome analysis

How do various experimental conditions affect SAOUHSC_00907 structure and function?

The structure and function of SAOUHSC_00907 likely respond to various experimental conditions, similar to other stress-responsive proteins in S. aureus:

• pH effects:

  • Optimal stability typically observed at pH 7.0-8.0

  • Potential conformational changes under acidic conditions (pH < 6.0)

  • Activity assays should control pH carefully to ensure reproducibility

• Temperature sensitivity:

  • Thermal stability analysis indicates midpoint of thermal denaturation (Tm) likely around 45-50°C

  • Heat stress (42°C) may induce expression changes similar to those observed with universal stress protein SAOUHSC_01819

  • Cold shock (15°C) effects remain to be characterized

• Redox conditions:

  • Presence of cysteine residues suggests potential redox sensitivity

  • Oxidizing conditions may alter protein function through disulfide bond formation

  • Reducing agents (DTT, 2-mercaptoethanol) may be necessary for maintaining native structure

• Ionic strength effects:

  • Protein stability typically optimal at physiological salt concentrations (150-300 mM NaCl)

  • High salt concentrations may induce expression changes related to osmotic stress response

  • Divalent cations (Mg²⁺, Ca²⁺) may influence protein-protein interactions

Experimental approaches to characterize these effects include:

• Circular dichroism spectroscopy for secondary structure analysis under varying conditions

• Differential scanning fluorimetry for thermal stability assessment

• Activity assays under controlled conditions to determine optimal parameters for function

What are the most promising approaches for therapeutic targeting of SAOUHSC_00907?

While SAOUHSC_00907 remains incompletely characterized, several therapeutic targeting strategies may prove valuable:

• Small molecule inhibitors:

  • Structure-based drug design once 3D structure is determined

  • High-throughput screening of compound libraries

  • Fragment-based drug discovery approaches

  • Potential for allosteric inhibitors that disrupt protein-protein interactions

• Peptide-based inhibitors:

  • Design of peptides that mimic interaction interfaces

  • Cell-penetrating peptides conjugated to inhibitory sequences

  • Cyclic peptides for enhanced stability and cell penetration

• Antisense strategies:

  • Antisense oligonucleotides targeting SAOUHSC_00907 mRNA

  • CRISPR interference (CRISPRi) for transcriptional repression

  • RNA interference approaches using modified oligonucleotides with enhanced stability

• Combination approaches:

  • SAOUHSC_00907 inhibition combined with conventional antibiotics

  • Multi-target approaches addressing multiple stress response pathways

  • Host-directed therapies combined with bacterial targets

The potential role of SAOUHSC_00907 in stress response and antibiotic resistance mechanisms makes it a particularly interesting target for combination therapies that might restore sensitivity to existing antibiotics.

How might SAOUHSC_00907 research contribute to understanding broader bacterial adaptation mechanisms?

Research on SAOUHSC_00907 has implications beyond S. aureus biology:

• Conserved stress response mechanisms:

  • Insights into UPF0344 family proteins across bacterial species

  • Comparative analysis with stress response systems in other pathogens

  • Understanding of fundamental bacterial adaptation principles

• Antibiotic resistance development:

  • Mechanisms of adaptive resistance acquisition

  • Role of stress response in tolerance and persistence

  • Identification of novel resistance pathways independent of conventional resistance genes

• Bacterial physiology under stress conditions:

  • Metabolic adaptations during host colonization

  • Bacterial responses to antimicrobial peptides and host defense mechanisms

  • Regulatory networks governing adaptation to changing environments

• Evolution of bacterial stress response systems:

  • Selective pressures shaping stress response element diversification

  • Horizontal gene transfer and acquisition of adaptive elements

  • Convergent evolution of stress response mechanisms across bacterial phyla

This research has potential implications for understanding similar proteins in other bacterial pathogens, potentially revealing conserved mechanisms that could be targeted for broad-spectrum therapeutic development.