Randall K. Holmes

Professor, Chair M.D., Ph.D., New York University

Current Research

Our laboratory uses molecular methods to study the genetics and regulation of bacterial protein toxins, their roles in pathogenesis of infectious diseases, and their uses for vaccine development. The toxins and regulatory proteins currently being studied include diphtheria toxin from Corynebacterium diphtheriae, cholera toxin from Vibrio cholerae, type I and type II heat-labile enterotoxins from Escherichia coli, the diphtheria toxin repressor (DtxR) from Corynebacterium diphtheriae, and the homologous iron-dependent regulator (IdeR) from Mycobacterium tuberculosis.

Diphtheria toxin causes the serious manifestations of diphtheria. DtxR is an iron-activated regulatory protein that negatively controls synthesis of diphtheria toxin and other putative virulence factors of C. diphtheriae. We cloned the dtxR gene from C. diphtheriae and the ideR gene from M. tuberculosis. We purified and characterized DtxR and IdeR in vitro, identified the consensus sequence for DtxR-regulated operators, and determined the crystal structures of DtxR as an apo-repressor, a holo-repressor and a holo-repressor in complex with DNA. Current studies in our laboratory focus on identifying the molecular basis for interactions of DtxR and IdeR with DNA, characterizing the DtxR-specific regulon in C. diphtheriae by genetic, proteomic and microarray-based transcriptional analyses, identifying the importance of DtxR-regulated genes in the pathogenesis of diphtheria, and developing compounds that modulate the biological activities of IdeR as potentially novel therapeutic agents against tuberculosis.

Cholera toxin and the closely related E. coli heat-labile enterotoxins cause the secretory diarrhea of cholera and traveler’s diarrhea, respectively. These toxins consist of a pentameric B subunit that binds to ganglioside receptors on target cells and a monomeric A subunit that activates adenylate cyclase by ADP-ribosylation of the regulatory protein Gs. Current studies in our laboratory are analyzing the structure and function of these enterotoxins in vitro and the mechanisms for their uptake and trafficking in target cells. CT is also a potent mucosal antigen and immunomodulatory agent. We have developed methods to make cholera toxin-like chimeric proteins in which the enzymatic domain of the native A polypeptide is replaced by various other microbial protein antigens. We are testing them as experimental vaccines to determine whether they can present the foreign antigenic domains to the mucosal immune system in a highly immunogenic manner.

Recent Publications

Click Here For An Updated List Of Dr. Holmes' Publications

Wisedchaisri, G., C.J. Chou, M. Wu, C. Roach, A.E. Rice, R.K. Holmes, C. Beeson and W.G.J. Hol. 2007. Crystal structures, metal-activation and DNA-binding properties of two-domain IdeR from Mycobacterium tuberculosis. Biochemistry 46:436-447.

Oram, M., J.E. Woolston, A.D. Jacobson, R.K. Holmes, and D.M. Oram. 2007. Bacteriophage-based vectors for site-specific insertion of DNA in the chromosome of corynebacteria. Gene 391:53-62.

Schonteich, E., M. Pilli, G.C. Simon, H.T. Matern, J.R. Junutula, D. Sentz, R.K. Holmes and R. Prekeris. 2007. Molecular Characterization of RAB11-FIP3 Binding to ARF GTPases. European Journal of Cell Biology 86:417-431.

Teter, K., M.G. Jobling, D. Sentz, and R.K. Holmes. 2006. The cholera toxin A13 subdomain is essential for interaction with ADP-ribosylation factor 6 and full toxic activity but is not required for translocation from the endoplasmic reticulum to the cytosol. Infect. Immun. 74:2259-2267.

Oram, D.M., A.D. Jacobson, and R.K. Holmes. 2006. Transcription of the contiguous sigB, dtxR and galE genes in Corynebacterium diphtheriae: evidence for multiple transcripts and regulation by environmental factors. J. Bacteriol. 188:2959-2973.

Oram, D.M., and R.K. Holmes. 2006. Diphtheria toxin, Chapter 13, p245-256. In J.E. Alouf and M.R. Popoff, eds., Comprehensive Sourcebook of Bacterial Protein Toxins, 3rd Edition, Elsevier Ltd.

Jobling, M.G., and R.K. Holmes. 2006. Heat-labile enterotoxins. In R. Curtiss III (Editor in Chief), EcoSalEscherichia coli and Salmonella: Cellular and Molecular Biology. [Online:] http://www.ecossal.org. ASM Press, Washington, DC.

Gilbert, J., J. Dahl, C. Riney, J. You, C. Cui, R. Holmes, W. Lencer, and T. Benjamin. 2005. Ganglioside GD1a restores infectability to mouse cells lacking functional receptors for polyoma virus. J. Virol. 79:615-618.

Oram, D.M., L.M. Must, J.K. Spinler, E.M. Twiddy and R.K. Holmes. 2005. Repressor activity and antigenicity of the iron dependent transcriptional regulators from Corynebacterium diphtheriae and Mycobacterium tuberculosis. FEMS Microbiol. Lett. 243:1-8.

Tinker, J.K., J. Erbe, and R.K. Holmes. 2005. Characterization of fluorescent chimeras of cholera toxin and Escherichia coli heat labile enterotoxins produced by use of the twin arginine translocation system. Infect. Immun. 73:3627-3635.

Guerra, L., K. Teter, B.N. Lilley, B. Stenerlöw, R.K. Holmes, H.L. Ploegh, K. Sandvig, M. Thelestam and T. Frisan. 2005. Cellular internalization of cytolethal distending toxin: a new end to a known pathway. Cellular Microbiol. 7:921-934.

O’Neal, C.J., M.G. Jobling, R.K. Holmes, and W.G.J. Hol. 2005. Structural basis for the activation of cholera toxin by human ARF6-GTP. Science 309:1093-1096.