STRUCTURE AND MECHANISM OF CS1 PILUS ASSEMBLY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Pili are hair-like surface fibers that mediate attachment and colonization of pathogenic bacteria to host tissues. The CS1 pilus system from enterotoxigenic Escherichia coli (ETEC) is required for the establishment and colonization of ETEC to the human intestine, resulting in diarrheal disease that is a significant cause of morbidity in infants and children in third-world countries. CS1 is encoded on the cooBACD operon, and is composed of multiple CooA subunits that have at the distal tip the single subunit of CooD that is required for adherence to intestinal cells. Additionally, CooC, a 95-kDa outer membrane protein, and CooB, a periplasmic chaperone, are required for pilus assembly. The specific hypothesis is that the assembly of CS1 pili is initiated by a conformational change in the outer membrane protein CooC upon binding of CooB alone are as a complex with CooD or CooA. The hypothesis is based on data that indicate that 1) CooC is an integral outer membrane protein, 2) expression of CooC is required for export of pili to the cell surface and 3) CooB co-purifies with CooC and stabilizes CooC against proteolytic degradation. Therefore CooB, either by itself or as a complex with CooA or CooD, initiates a conformational change in CooC that allows transport of subunits to the surface. The specific aims of our research are: 1. Characterize the native structure and oligomerization state of CooB. 2. Define structural changes in CooC. 3. Determine the role of CooC in the mechanism of polymerization of CooA. Information obtained from these studies may be useful in the design of novel therapies that provide protection against ETEC infection.