Recombinant Staphylococcus aureus UPF0365 protein SAS1511 (SAS1511)

What is UPF0365 protein SAS1511 and what organism does it come from?

UPF0365 protein SAS1511 is a protein from Staphylococcus aureus strain MSSA476, a methicillin-susceptible strain of this important human pathogen. It belongs to the UPF0365 protein family, which consists of proteins with unknown function that are found across multiple bacterial species. The specific designation SAS1511 refers to its locus tag in the S. aureus MSSA476 genome sequence. The full-length protein comprises 329 amino acids and appears to be associated with membrane function based on its sequence characteristics .

What are the optimal storage conditions for recombinant SAS1511 protein?

For optimal stability, recombinant SAS1511 protein should be stored at -20°C for routine use. For long-term storage, maintaining the protein at -20°C or preferably -80°C is recommended. The commercial preparation is typically provided in a Tris-based buffer containing 50% glycerol to prevent freeze damage. Working aliquots can be stored at 4°C for up to one week to minimize freeze-thaw cycles, as repeated freezing and thawing is not recommended and may lead to protein degradation and loss of activity .

How is recombinant SAS1511 protein typically produced?

Recombinant SAS1511 protein is typically produced using heterologous expression systems. While the specific expression system may vary depending on research needs, the protein can be expressed in E. coli, yeast, baculovirus, or mammalian cell systems. For basic biochemical studies, E. coli is often the preferred host due to its high yield and cost-effectiveness. The expression construct includes the coding sequence for the full-length protein (expression region 1-329) and may include purification tags that are determined during the production process .

What is the Uniprot identifier for SAS1511 protein and how can it be used in research?

The Uniprot identifier for SAS1511 protein is Q6G8Z4. This identifier serves as a critical reference point for researchers, providing access to curated information about the protein's sequence, predicted features, and known functions. When designing experiments involving SAS1511, researchers should consult this database entry to identify conserved domains, potential active sites, and predicted secondary structure elements that might inform functional studies or protein engineering approaches .

What buffer systems are commonly used for recombinant SAS1511 protein experiments?

Recombinant SAS1511 protein is typically stored in a Tris-based buffer containing 50% glycerol, optimized for protein stability. For experimental work, the choice of buffer depends on the specific application. Biochemical assays often employ phosphate-buffered saline (PBS) at physiological pH, while structural studies might require specialized buffers with controlled ionic strength. When designing functional assays, researchers should consider using buffers that mimic the bacterial environment, such as modified synthetic medium approximating the staphylococcal milieu, particularly when investigating potential membrane-associated functions .

What related UPF0365 family proteins exist in other S. aureus strains?

Several homologs of SAS1511 have been identified in different S. aureus strains, including:

• SAV1573 - Found in S. aureus strains like Mu50, this appears to be a partial homolog of SAS1511

• SAUSA300_1533 - Present in the USA300 strain, an important community-acquired methicillin-resistant S. aureus (CA-MRSA) strain

These proteins share sequence similarity with SAS1511 and are also classified as members of the UPF0365 protein family. The conservation of these proteins across multiple S. aureus strains suggests they may perform important functions in staphylococcal physiology or pathogenesis .

What experimental approaches can determine the specific function of SAS1511 in S. aureus?

Determining the function of UPF0365 family proteins like SAS1511 requires a multi-faceted approach:

• Gene knockout and complementation studies: Create SAS1511 deletion mutants in S. aureus MSSA476 and assess phenotypic changes in growth, stress response, and virulence. Complementation with wild-type SAS1511 should restore the original phenotype.

• Transcriptomic and proteomic analyses: Compare gene expression and protein profiles between wild-type and SAS1511 knockout strains under various conditions to identify affected pathways.

• Protein-protein interaction studies: Use pull-down assays, bacterial two-hybrid systems, or proximity labeling approaches to identify interaction partners of SAS1511.

• Structural analysis: Determine the three-dimensional structure of SAS1511 using X-ray crystallography or NMR spectroscopy to gain insights into potential functions based on structural similarities to proteins of known function.

• Subcellular localization: Use fluorescent protein fusions or immunolocalization to determine where SAS1511 resides within the bacterial cell, which may provide functional clues.

These complementary approaches can collectively provide insights into the biological role of this uncharacterized protein in S. aureus physiology and pathogenesis.

What is the potential role of SAS1511 in S. aureus pathogenicity?

While the specific role of SAS1511 in S. aureus pathogenicity remains to be definitively established, several lines of investigation are warranted:

• Virulence model testing: Compare the virulence of wild-type and SAS1511-deficient strains in appropriate animal models of S. aureus infection, including skin and soft tissue infection, bacteremia, and endocarditis models.

• Host-pathogen interaction studies: Assess whether SAS1511 affects interactions with host cells or immune components using in vitro infection models with relevant human cell types.

• Stress response evaluation: Determine if SAS1511 contributes to bacterial survival under host-relevant stress conditions, such as oxidative stress, antimicrobial peptides, or nutrient limitation.

• Comparative genomics: Analyze the conservation and variation of SAS1511 across clinical isolates with different virulence profiles to identify correlations between protein sequence and pathogenic potential.

The membrane-associated nature of SAS1511, as suggested by its amino acid sequence, indicates it may function at the interface between the bacterium and its environment, potentially influencing pathogen-host interactions that are critical for virulence .

How can recombinant SAS1511 be used in vaccine development against S. aureus infections?

Given the challenges in developing effective S. aureus vaccines, incorporating SAS1511 into vaccine strategies requires careful consideration:

• Antigenicity assessment: Evaluate if SAS1511 is immunogenic during natural S. aureus infection by screening patient sera for anti-SAS1511 antibodies.

• Epitope mapping: Identify immunodominant epitopes within SAS1511 that might elicit protective antibody responses.

• Multicomponent vaccine design: Consider SAS1511 as one component of a multicomponent vaccine, similar to the approach taken with the rFSAV vaccine that combines five S. aureus antigens (Hla, SEB, MntC, IsdB, and SpA) .

• Protein conjugation strategy: If pursuing a glycoconjugate approach, consider conjugating SAS1511 to S. aureus capsular polysaccharides rather than using carrier proteins from unrelated bacteria, as this "designer" approach has shown improved immunogenicity in recent studies .

• Functional antibody testing: Assess whether antibodies against SAS1511 promote opsonophagocytosis or neutralize any potential virulence-associated functions of the protein.

Previous vaccine development efforts against S. aureus have faced significant challenges, with several high-profile failures. Recent research suggests that effective vaccines may need to target multiple antigens and elicit both humoral and cellular immune responses .

What methodologies can be used to study protein-protein interactions involving SAS1511?

Several complementary approaches can be employed to identify and characterize protein-protein interactions involving SAS1511:

• Co-immunoprecipitation (Co-IP): Using antibodies against SAS1511 or epitope tags in pull-down experiments followed by mass spectrometry to identify interacting partners.

• Bacterial two-hybrid (B2H) analysis: Adapting yeast two-hybrid principles to bacterial systems to screen for potential interaction partners in vivo.

• Surface plasmon resonance (SPR): Measuring binding kinetics and affinity between purified SAS1511 and candidate interaction partners.

• Proximity-dependent biotin labeling: Using BioID or APEX2 fusions with SAS1511 to identify proteins in close proximity within the native bacterial environment.

• Cross-linking mass spectrometry: Employing chemical cross-linkers to stabilize transient interactions followed by mass spectrometry analysis to identify interaction sites.

When interpreting interaction data, researchers should consider that SAS1511's apparent membrane association may require specialized approaches to maintain the protein in its native conformation during experimental manipulation .

What are the challenges in expressing and purifying full-length SAS1511 protein?

Expressing and purifying the full-length SAS1511 protein (329 amino acids) presents several technical challenges:

• Membrane protein solubility: The hydrophobic N-terminal region of SAS1511 suggests it may be membrane-associated, potentially requiring detergents or specialized solubilization strategies for effective purification.

• Expression system selection: While E. coli is commonly used, the presence of transmembrane domains may necessitate eukaryotic expression systems like yeast or insect cells that provide more sophisticated membrane protein processing capabilities.

• Protein folding and stability: Ensuring proper folding of both membrane and soluble domains may require optimization of expression conditions, including temperature, induction protocols, and folding aids.

• Purification strategy optimization: The choice between affinity tags (His, GST, MBP) should be made based on protein solubility and function, with consideration for whether the tag needs to be removed for downstream applications.

• Quality control assessment: Verifying proper folding and function through biochemical and biophysical techniques like circular dichroism, size exclusion chromatography, and functional assays is essential before proceeding to experimental applications.

Commercial preparations typically achieve >90% purity, suggesting that despite these challenges, high-quality protein can be obtained with optimized protocols .