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Nancy Martin

 
  Associate Professor

 
  Contact Information:  
  Department of Microbiology & Immunology,
Botterell Hall Rm 740,
Queen's University,
Kingston, Ontario,
K7L 3N6, Canada Tel: (613) 533-2460
Fax: (613) 533-6796
E-mail: NLM@queensu.ca


 
  Several years ago we initiated an effort to characterize the disulphide oxidoreductases of Salmonella enterica serovar Typhimurium and found two periplasmic “foldases” that act to assist protein folding and are especially important to cell function when bacteria are growing in stressful conditions. One is a homologue of DsbA from E.coli, an enzyme that has been crystallized and has undergone extensive biochemical analysis. The second enzyme, called SrgA, is a substrate specific disulphide oxidoreductase that functions to oxidize cysteine resides in the PEF pilin subunit. As this work progressed we became interested in the transcriptional regulation of these foldases and this led to our current work studying the regulation of stress response proteins in S. typhimurium via a two component histidine kinase signal transduction pathway.

Bacteria survive in a multitude of diverse niches within the host organism and the ability to adapt to the specific challenges presented by each of these niches is key to establishing infection. Bacterial utilize several histidine kinase signal transduction pathways to sense and respond to changes outside of the cell. The lab currently focuses on two central issues related to sensing and responding to environmental stresses mediated by the Cpx histidine kinase pathway in S. typhimurium. First, we are attempting to map the types of environmental signals that stimulate specific stress response pathways. Using a proteomic-based approach coupled with transcriptional analysis of specific Cpx-responders we are comparing the responses of wild type and various mutant strains to a variety of stressors. Second, we are using a combined proteomic and biochemical approach to identify downstream responses in the Cpx signal transduction pathway. For example, we believe that a serine/threonine kinase is responsible for propagating the Cpx-initiated signal along one branch of the Cpx pathway. Serine/threonine kinases are poorly understood in bacterial systems, however our work is leading to an appreciation of how posttranslational events such as phosphorylation play a central role in bacterial adaptation and survival in the host. These studies will greatly enhance our understanding of bacterial virulence mechanisms and show us, perhaps, new approaches to controlling organisms that cause infectious disease.



 
  Publications:  
  Suntharalingam, P., H. Spencer, C.V. Gallant, and N.L. Martin. 2003. Salmonella typhimurium rdoA is growth phase regulated and involved in relaying Cpx induced signals. J. Bacteriol. 185:432-443 (This publication utilized PFD facility resources)

Bouwman, C. W., M. Kohli, A. Killoran, G. Touchie, R. J. Kadner, and N.L. Martin. 2003. Characterization of SrgA, a Salmonella typhimurium virulence plasmid-encoded paralogue of the disulfide oxidoreductase DsbA essential for PEF pilus biogenesis. J. Bacteriol. 185:991-1000

Roberts, M.D., N.L. Martin, and A.M. Kropinski. 2004. The genome and proteome of coliphage T1. Virology 318:245-266 (This publication utilized PFD facility resources)

Gallant, C.V., T. Ponnampalam, H. SPencer, J.C.D. Hinton, and N.L. Martin. 2004. H-NS represses Salmonella enterica serovar typhimurium dsbA expression during exponential growth. J. Bacteriol. 186:910-918

Martin, N.L. A proteome reference map of soluble proteins for Salmonella enterica Serovar Typhimurium. (in revision) (This publication utilized PFD facility resources)

Zheng J., C. He, V. Singh, N.L. Martin, and Z. Jia. 2006. Crystallization of a novel prokaryotic Ser/Thr kinase and its implication in the Cpx stress response pathway. Molec. Microbiol. 63(5):1360-1371.

Martin, N.L. 2007. Sequence plus structure plus experimental inquiry: combining the clues to elucidate bacterial kinase function. Future Microbiol. 2(3):223-226