Primary Appointment:
 Microbiology & Immunology

GEBS Cluster Affiliations:
 Immunology, Microbiology, and Virology - IMV

University of Rochester
School of Medicine and Dentistry
601 Elmwood Ave, Box 672
Rochester, New York 14642

Medical Center 2-3009
Phone: (585) 275-0680
E-Mail: rips@uhura.cc.rochester.edu

Genetics and Analysis of the Polysialic Acid Gene Cluster of E coli K1

Capsular polysaccharides are the outermost structures on the bacterial cell and play a critical role in the interaction between the microorganism and its environment. Capsules are important virulence determinants of bacteria, and provide the bacterium with mechanisms to avoid an array of host defenses. The K1 capsule confers invasiveness to Escherichia coli, the most common gram negative organism causing meningitis during the neonatal period.

The goal of our research is to elucidate the molecular and genetic events controlling the synthesis, assembly, and transport of the K1 capsule, an alpha-2,8-linked polymer of sialic acid (polySia). These activities are encoded by the 17-kb kps gene cluster which is divided into three functional regions. The central region 2 is unique for a given polysaccharide antigen and contains information for synthesis, activation, and polymerization of sialic acid. In contrast, genes in regions 1 and 3 are conserved among E. coli synthesizing serologically distinct capsules. Region 1 encodes gene products that function in the transport of polymer across the outer membrane to the cell surface. Region 3 encodes two proteins, KpsM and KpsT, that constitute a system for transport of polySia across the cytoplasmic membrane. KpsM is a hydrophobic integral inner membrane protein, while KpsT is a peripheral inner membrane protein that binds ATP. They belong to the ATP-binding cassette (ABC) superfamily of transporters. Current research focuses on (1) the role of NeuD, a region 2 gene product, in polySia synthesis and (2) the role of KpsT in chain translocation.

Vann WF, Daines DA, Murkin AS, Tanner ME, Chaffin DO, Rubens CE, Vionnet J, Silver RP. The NeuC protein of Escherichia coli K1 is a UDP N-acetylglucosamine 2-epimerase. J Bacteriol. 186:706-12, 2004.

Nsahlai CJ, Silver RP. Purification and characterization of KpsT, the ATP-binding component of the ABC-capsule exporter of Escherichia coli K1. FEMS Microbiol Lett 224:113-8, 2003.

Daines DA, Granger-Schnarr M, Dimitrova M, Silver RP. Use of LexA-based system to identify protein-protein interactions in vivo. Methods Enzymol. 358:153-61, 2002.

Silver RP, Prior K, Nsahlai C, Wright LF. ABC transporters and the export of capsular polysaccharides from gram-negative bacteria. Res Microbiol. 152:357-64, 2001.

Bacon DJ, Szymanski CM, Burr DH, Silver RP, Alm RA, Guerry P. A phase-variable capsule is involved in virulence of Campylobacter jejuni 81-176. Mol Microbiol. 40:769-77, 2001.

Daines DA, Silver RP. Evidence for Multimerization of Neu Proteins Involved in Polysialic Acid Synthesis in Escherichia coli K1 Using Improved LexA-Based Vectors. J Bacteriol. 182:5267-5270, 2000.

Pigeon RP, Silver RP. Analysis of the G93E mutant allele of KpsM, the membrane component of an ABC transporter involved in polysialic acid translocation in Escherichia coli K1. FEMS Microbiology Lett 156:217-22, 1997.

Vann WF, Tavarez JJ, Crowley J, Vimr E, Silver RP. Purification and characterization of the Escherichia coli K1 neuB gene product N-acetylneuraminic acid synthetase. Glycobiology 7:697-701, 1997.

Bliss JM, Silver RP. Evidence that KpsT, the ATP-binding component of an ATP-binding cassette transporter, is exposed to the periplasm and associates with polymer during translocation of the polysialic acid capsule of Escherichia coli K1. J Bacteriol 179:1400-3, 1997.