Structural and functional studies of the heptose modifying enzymes that play a role in Campylobacter jejuni virulence.
Abstract
Campylobacter jejuni is a major cause of gastroenteritis in humans. The capsule of some species contains unique modified heptoses. Heptose modification was elucidated for C. jejuni NCTC11168 and 18-176, and novel epimerases and reductases essential for the heptose modification were identified. We hypothesized that heptose modifying enzymes in C. jejuni have specific catalytic residues that allow for substrate and product specificity. Substrate synthesis, structural modeling, point mutations, and enzymatic analysis have been applied to map the active sites. Putative catalytic residues showed substrate and/or product specificity. The epimerases structures were solved by crystallography done by our collaborator. We also hypothesized that synthesis of the modified heptoses is important for biofilm formation. In vitro experiment of C. jejuni NCTC11168 showed that the heptose biosynthesis mutants have a significant reduction in biofilm formation under aerobic conditions. This project has provided essential information about the structure and mechanism of heptose modifying enzymes. It also will emphasize their importance in C. jejuni virulence.