The Walker Lab works in two major areas.
We are working to develop a comprehensive understanding of the bacterial cell envelope – how it is assembled, how it changes in response to stress, and what its key vulnerabilities are – and to exploit this understanding to identify small molecules that inhibit cell envelope targets. Our goal is to contribute new knowledge, innovative methods, and compounds for use to combat antibiotic resistance. Pathogens of primary interest include MRSA and Streptococcus pneumoniae.
We are also working to elucidate the chemistry of O-GlcNAc transferase (OGT) and to develop genetic methods and small molecules to manipulate OGT in mammalian cells. Our goal is to use separation-of-function mutants and selective inhibitors to deconvolute OGT’s complex biology and assess its potential as a therapeutic target.
Approaches: Biochemistry (pathway reconstitution, target characterization, compound mechanism of action), genetics (evaluation of cellular function), high throughput screening (inhibitor discovery), systems biology (genome-wide perturbation analysis of antimicrobial compounds; other –omics approaches applied to small molecules).
Recent papers that feature cell envelope-related research:
Pasquina L, Santa Maria JP, McKay Wood B, Moussa SH, Matano LM, Santiago M, Martin SES, Lee W, Meredith TC, Walker S. "A synthetic lethal approach for compound and target identification in Staphylococcus aureus." Nat Chem Biol. 2016;12 :40-5.
Schaefer K, Matano LM, Qiao Y, Kahne D, Walker S. "In vitro reconstitution demonstrates the cell wall ligase activity of LCP proteins." Nat Chem Biol. 2017;13 :396-401.
Matano LM, Morris HG, Hesser AR, Martin SES, Lee W, Owens TW, Laney E, Nakaminami H, Hooper D, Meredith TC, et al. "Antibiotic That Inhibits the ATPase Activity of an ATP-Binding Cassette Transporter by Binding to a Remote Extracellular Site." J Am Chem Soc. 2017;139 :10597-10600.
Qiao Y, Srisuknimit V, Rubino F, Schaefer K, Ruiz N, Walker S, Kahne D. "Lipid II overproduction allows direct assay of transpeptidase inhibition by β-lactams." Nat Chem Biol. 2017;13 :793-798.
Welsh MA, Taguchi A, Schaefer K, Van Tyne D, Lebreton F, Gilmore MS, Kahne D, Walker S. "Identification of a Functionally Unique Family of Penicillin-Binding Proteins." J Am Chem Soc. 2017;139 :17727-17730.
Vickery CR, Wood MKB, Morris HG, Losick R, Walker S. "Reconstitution of Staphylococcus aureus Lipoteichoic Acid Synthase Activity Identifies Congo Red as a Selective Inhibitor." J Am Chem Soc. 2018.
Selected OGT papers:
Lazarus MB, Nam Y, Jiang J, Sliz P, Walker S. "Structure of human O-GlcNAc transferase and its complex with a peptide substrate." Nature. 2011;469 :564-7.
Lazarus MB, Jiang J, Gloster TM, Zandberg WF, Whitworth GE, Vocadlo DJ, Walker S. "Structural snapshots of the reaction coordinate for O-GlcNAc transferase." Nat Chem Biol. 2012;8 :966-8.
Lazarus MB, Jiang J, Kapuria V, Bhuiyan T, Janetzko J, Zandberg WF, Vocadlo DJ, Herr W, Walker S. "HCF-1 is cleaved in the active site of O-GlcNAc transferase." Science. 2013;342 :1235-9.
Ortiz-Meoz RF, Jiang J, Lazarus MB, Orman M, Janetzko J, Fan C, Duveau DY, Tan Z-W, Thomas CJ, Walker S. "A Small Molecule That Inhibits OGT Activity in Cells." ACS Chem Biol. 2015;10 :1392-7.
Janetzko J, Trauger SA, Lazarus MB, Walker S. "How the glycosyltransferase OGT catalyzes amide bond cleavage." Nat Chem Biol. 2016;12 :899-901.
Janetzko J, Walker S. "Aspartate Glycosylation Triggers Isomerization to Isoaspartate." J Am Chem Soc. 2017;139 :3332-3335.