Screening and Analysis of Inhibitors against Staphylococcal Superantigen-like Protein 7
Andersin, Micaela (2024)
2024
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2024030710355
https://urn.fi/URN:NBN:fi-fe2024030710355
Tiivistelmä
Staphylococcus aureus (S. Aureus) can infect, colonize and survive in its host, utilizing 40 immune evasion proteins found up to date. By doing so it can cause a wide range of diseases including skin infections, sepsis or endocarditis. Furthermore, strains of S. aureus have developed a concerning amount of antibiotic resistance, presenting threats against human health today.
Staphylococcal superantigen-like protein 7 (SSL7) is a bifunctional immune evading protein secreted by S. aureus. It can inhibit two parts of the immune response by binding to human immunoglobulin A (IgA) and complement component 5 (C5). This bifunctionality and the antibiotic resistance of S. aureus makes SSL7 an attractive drug target to fight against infections caused by the bacterium.
SSL7 binds IgA by its oligonucleotide binding (OB) site, preventing it from recognizing S. aureus cells. This way IgA will not be able to bind to S. aureus and further be recognized by the IgA fragment crystallizable receptor. The receptor recognizes IgA-pathogen complexes, such as S. aureus–IgA complexes, and promotes their elimination. Additionally, by binding to C5, SSL7 inhibits its cleavage by C5 convertase to C5a and C5b. This halts the downstream pathway responsible for S. aureus elimination, as C5a is responsible for activation of neutrophils.
Utilizing structure-based drug design, peptides and macrocycles were screened against IgA and C5 binding sites of SSL7, to find ones that show potential inhibitory effect against the protein. Methods such as molecular docking, binding energy calculations and molecular dynamics simulation were used to rank these ligands and analyze their estimated binding properties in the SSL7 binding sites. To validate the predicted binding of top ranked hits against SSL7, the protein was expressed in Escherichia coli to further study the ligand binding in an enzyme-linked immunosorbent assay.
Seven peptides and nine macrocycles were predicted to have promising binding affinity towards SSL7. The peptides were predicted to stabilize and cover the C5 binding site, while macrocycles were preferred at the IgA binding site. These 16 ligands were selected for experimental studies (enzyme-linked immunosorbent assay) to validate their predicted binding activity against SSL7.
Staphylococcal superantigen-like protein 7 (SSL7) is a bifunctional immune evading protein secreted by S. aureus. It can inhibit two parts of the immune response by binding to human immunoglobulin A (IgA) and complement component 5 (C5). This bifunctionality and the antibiotic resistance of S. aureus makes SSL7 an attractive drug target to fight against infections caused by the bacterium.
SSL7 binds IgA by its oligonucleotide binding (OB) site, preventing it from recognizing S. aureus cells. This way IgA will not be able to bind to S. aureus and further be recognized by the IgA fragment crystallizable receptor. The receptor recognizes IgA-pathogen complexes, such as S. aureus–IgA complexes, and promotes their elimination. Additionally, by binding to C5, SSL7 inhibits its cleavage by C5 convertase to C5a and C5b. This halts the downstream pathway responsible for S. aureus elimination, as C5a is responsible for activation of neutrophils.
Utilizing structure-based drug design, peptides and macrocycles were screened against IgA and C5 binding sites of SSL7, to find ones that show potential inhibitory effect against the protein. Methods such as molecular docking, binding energy calculations and molecular dynamics simulation were used to rank these ligands and analyze their estimated binding properties in the SSL7 binding sites. To validate the predicted binding of top ranked hits against SSL7, the protein was expressed in Escherichia coli to further study the ligand binding in an enzyme-linked immunosorbent assay.
Seven peptides and nine macrocycles were predicted to have promising binding affinity towards SSL7. The peptides were predicted to stabilize and cover the C5 binding site, while macrocycles were preferred at the IgA binding site. These 16 ligands were selected for experimental studies (enzyme-linked immunosorbent assay) to validate their predicted binding activity against SSL7.