Cell wall biosynthesis
Some of the world's most important antibiotics, including the beta-lactams and vancomycin, target the bacterial cell wall, or peptidoglycan. These drugs have not only saved countless lives, they also have served as chemical probes for understanding cell wall biology. We hope that studying the pathways targeted by these compounds will enable the development of new antibiotics and lead to a better understanding of cell wall physiology.
Cell wall overview
Lipid II, the monomer for bacterial cell wall, is synthesized inside the cytoplasm and then flipped outward by the transporter MurJ. It is then polymerized by glycosyltransferases (GTs) and crosslinked by transpeptidases (TPs) to make the protective mesh that is cell wall.
Because the cell must grow and divide, peptidoglycan must be dynamic while simultaneously maintaining its structural integrity. Additionally, structural properties of peptidoglycan such as glycan chain length, degree of crosslinking, and sites of chemical modification appear to be carefully controlled by the cell. To achieve this, the cell organizes its cell wall-building proteins into complexes that modulate and coordinate their activities. Although the enzymatic functions of individual proteins are often known, it is crucial to understand their activities as members of complexes, which represents their true role in the living cell. We aim to discover new ways to break cell wall synthesis by better understanding how these complexes function.
Banner image: Crystal structure of the wall teiochoic acid ligase TagT and its substrate (Schaefer & Owens et al. JACS 2018)
Membrane potential is required for MurJ function. F.A. Rubino, S. Kumar, N. Ruiz, S. Walker, D. Kahne. J Am Chem Soc 2018; 140:4481-4.
Lipid II overproduction allows direct assay of transpeptidase inhibition by beta-lactams. Y. Qiao, V. Srisuknimit, F. Rubino, K. Schaefer, N. Ruiz, S. Walker, D. Kahne. Nat Chem Biol 2017; 13:793-8.
Reconstitution of peptidoglycan cross-linking leads to improved fluorescent probes of cell wall synthesis. M.D. Lebar, J.M. May, A.J. Meeske, S.A. Leiman, T.J. Lupoli, H. Tsukamoto, R. Losick, D.Z. Rudner, S. Walker, D. Kahne. J Am Chem Soc 2014; 136:10874-7.
Forming crosslinked peptidoglycan from synthetic Gram-negative Lipid II. M.D. Lebar, T.J. Lupoli, H. Tsukamoto, J.M. May, S. Walker, D.E. Kahne. J Am Chem Soc 2013; 135:4632-5.
Transpeptidase-Mediated Incorporation of d-Amino Acids into Bacterial Peptidoglycan. T.J. Lupoli, H. Tsukamoto, E.H. Doud, T.S. Wang, S. Walker, D. Kahne. J Am Chem Soc 2011; 133:10748-51.