title: Equilibrium of sortase A dimerization on Staphylococcus aureus cell surface mediates its cell wall sorting activity.
abstract: Staphylococcus aureus sortase A (SrtA) transpeptidase is a therapeutically important membrane-bound enzyme in Gram-positive bacteria, which organizes the covalently attached cell surface proteins on the peptidoglycan cell wall of the organism. Here, we report the direct observation of the highly selective homo-dimerization of SrtA on the cell membrane. To address the biological significance of the dimerization towards enzyme function, site-directed mutagenesis was performed to generate a SrtA mutant, which exists as monomer on the cell membrane. We observed that the cell surface display of adhesive proteins in S. aureus cells expressing monomeric SrtA mutant is more prominent than the cells expressing the wild-type enzyme. A cell-based invasion assay was also performed to evaluate the activities of wild-type SrtA and its monomeric mutant as well. Our data demonstrated that S. aureus cells expressing SrtA in monomeric form invade host mammalian cells more efficiently than those expressing wild-type SrtA in dimer-monomer equilibrium. The results suggested that the monomeric form of SrtA is more active than the dimeric form of the enzyme in terms of cell surface display of virulence factors for infection. This is the first study to present the oligomerization of SrtA and its related biological function on the cell membrane. Study of SrtA dimerization has implications for understanding its catalytic mechanism at the cellular level as well as the development of novel anti-infective agents.
authors.affiliation: Division of Medicinal Chemistry, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA Bioengineering Department, School of Engineering, Santa Clara University, Santa Clara, CA 95053, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Xiang
authors.affiliation: Division of Medicinal Chemistry, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA Department of Medicinal Chemistry, School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Faqin
authors.initials: F
authors.lastname: Jiang
authors.affiliation: Division of Medicinal Chemistry, College of Pharmacy, The University of Texas at Austin, Austin, TX 78712, USA Bioengineering Department, School of Engineering, Santa Clara University, Santa Clara, CA 95053, USA zzhang@scu.edu.
authors.forename: Zhiwen J
authors.initials: ZJ
authors.lastname: Zhang
mesh_terms: D018829:Adhesins, Bacterial / Q000378:metabolism; D019881:Aminoacyltransferases / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry / Q000201:enzymology*; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004705:Endocytosis; D004847:Epithelial Cells / Q000382:microbiology; D006801:Humans; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization; D013211:Staphylococcus aureus / Q000201:enzymology* / Q000235:genetics; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D050505:Mutant Proteins; D037521:Virulence Factors; D019881:Aminoacyltransferases; C120542:sortase A; D003546:Cysteine Endopeptidases
keywords: Sortase A; cell membrane; cell sorting activity; dimerization