The cell wall envelope of Gram-positive bacteria can be thought of as a microbial organelle with anchored surface proteins that require specific signals and targeting mechanism for their assembly. Previous work identified sortases, enzymes that recognize short peptide sequences within sorting signals of secreted proteins. Upon cleavage of a protein substrate immediately following a conserved threonine residue, sortases form a thioester acyl intermediate between the C-terminal carboxyl group of the substrate and their active site cysteine residue. This intermediate is subsequently resolved by the nucleophilic attack of an amino group, which completes the transpeptidation reaction and restores the active site of sortase. Four classes of sortases are distinguished on the basis of sequence homology and enzyme function. One of these, sortase A, cleaves all surface proteins harboring LPXTG sorting signals and tethers its products to the amino group of lipid II, the precursor of cell wall biosynthesis. In contrast, sortase D cleaves only the sorting signals of pilin subunits. By accepting the side chain amino group of lysine (K) within the YPKN motif of pilin precursors, sortase D assembles pili on the surface of Gram-positive bacteria. Bacillus cereus pili are formed from two subunits, the tip protein (BcpB) and the major pilin (BcpA), which generates the pilus shaft. Sortases A and D collaborate on the topic of pilus formation;their assembled product is immobilized in the cell wall and extends 0.3-1.5

Public Health Relevance

Gram-positive bacteria cause many different human diseases and the morbidity and mortality of these infections, largely due to the development of antibiotic resistance traits, continues to increase in the United States. By studying the molecular mechanisms whereby Gram-positive bacteria promote the anchoring and surface display of proteins that enable the pathogenesis of human infections, we aim to increase knowledge about infectious processes. By developing inhibitors that prevent the assembly of proteins in the bacterial envelope we aim to develop antiinfectives that may be useful for the treatment of human infections.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Prokaryotic Cell and Molecular Biology Study Section (PCMB)
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Huntley, Clayton C
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University of Chicago
Schools of Medicine
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Chan, Yvonne G Y; Frankel, Matthew B; Missiakas, Dominique et al. (2016) SagB Glucosaminidase Is a Determinant of Staphylococcus aureus Glycan Chain Length, Antibiotic Susceptibility, and Protein Secretion. J Bacteriol 198:1123-36
Missiakas, Dominique; Schneewind, Olaf (2016) Staphylococcus aureus vaccines: Deviating from the carol. J Exp Med 213:1645-53
Kim, Hwan Keun; Falugi, Fabiana; Missiakas, Dominique M et al. (2016) Peptidoglycan-linked protein A promotes T cell-dependent antibody expansion during Staphylococcus aureus infection. Proc Natl Acad Sci U S A 113:5718-23
Thomer, Lena; Schneewind, Olaf; Missiakas, Dominique (2016) Pathogenesis of Staphylococcus aureus Bloodstream Infections. Annu Rev Pathol 11:343-64
Thammavongsa, Vilasack; Kim, Hwan Keun; Missiakas, Dominique et al. (2015) Staphylococcal manipulation of host immune responses. Nat Rev Microbiol 13:529-43
Kim, Hwan Keun; Falugi, Fabiana; Thomer, Lena et al. (2015) Protein A suppresses immune responses during Staphylococcus aureus bloodstream infection in guinea pigs. MBio 6:
Becker, Samuel; Frankel, Matthew B; Schneewind, Olaf et al. (2014) Release of protein A from the cell wall of Staphylococcus aureus. Proc Natl Acad Sci U S A 111:1574-9
Zhang, Jie; Liu, Hongchuan; Zhu, Kongkai et al. (2014) Antiinfective therapy with a small molecule inhibitor of Staphylococcus aureus sortase. Proc Natl Acad Sci U S A 111:13517-22
Schneewind, Olaf; Missiakas, Dominique (2014) Sec-secretion and sortase-mediated anchoring of proteins in Gram-positive bacteria. Biochim Biophys Acta 1843:1687-97
Thomer, Lena; Becker, Samuel; Emolo, Carla et al. (2014) N-acetylglucosaminylation of serine-aspartate repeat proteins promotes Staphylococcus aureus bloodstream infection. J Biol Chem 289:3478-86

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