Chitin, the fibrous beta-1,4-linked polymer of N-acetylglucosamine, serves as a major structural component in fungi and numerous animal species, but is essentially absent from vertebrates. In yeast, its major function is to support the collar and septum that separates mother and budding daughter cell. In collaboration with others the P.I.'s laboratory has shown that yeast chitin is made by three separate enzymes, each encoded by a separate gene. Each enzyme has a specific site of localization and chitin deposition. Furthermore, in Saccharomyces a specific hydrolytic enzyme (chitinase) functions in the septal region and is required for separation of mother and daughter cell. Evidence suggests that organisms with more complex patterns of chitin deposition (e.g. filamentous fungi) have as many as six or seven chitin synthases, each with its specific function and localization. This concept of multiple synthases and lack of functional redundancy has important implications for use of chitin synthases as targets for antifungal drugs. In the coming grant period the P.I. will study the interactions among chitin synthase proteins and the other proteins of the mother-bud neck region by the two-hybrid technique, epitope tagging, and direct identification of the protein-protein interactions. Genetic analysis will also be important since it is anticipated that deletion of important members of the mother-bud neck complex will lead to delocalization of other members of the complex. As a second project in the chitin synthase area, the P.I. will start an exploration of synthases of nonfungal organisms e.g. insects, where chitin forms the core of key structural components such as the exoskeleton and intestinal peritrophic membrane. The P.I. will explore the role of chitin hydrolysis (chitinase action) in insect development and the life cycles of human parasites. Recent work suggests that in insects chitinases may function as growth factors as well as being involved in molting. In parasites, chitinases may play roles in important processes such as egg (cyst) hatching and penetration of the insect peritrophic membrane. Recent experiments by others have shown, in fact, that allosamidin, a very specific chitinase inhibitor, will block parasite peritrophic membrane penetration and transmission of malaria.
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