Our research involves the determination of three-dimensional structures of protein molecules to characterize and understand at the atomic level how these molecules function. Our interest is focused on two projects, 1) pectate-degrading enzymes, and 2) phosphatidylinositol transfer protein.
Microbial plant pathogens secrete a battery of enzymes to attack the plant. Pectate, an acidic saccharide, is one of the most enzymatically susceptible components of the plant cell wall. Pectate-degrading enzymes have been demonstrated to be virulence factors in plant diseases characterized by plant tissue degradation, in particular, soft rot diseases. There are two major families of pectate-degrading enzymes, the polygalacturonases (PG) and the pectate lyases (PL). Both enzymes act on the same substrate, pectate, but differ in their enzymatic mechanism; PG’s cleave by hydrolysis, PL’s by a B’-elimination mechanism. The protein fold of both enzymes is similar. We are probing the specifici amino acids that cause the differences in mechanism utilized by these two enzymes to cleave the same substrate bond.
Eukaryotic phosphatidylinositol transfer protein (PITP) is a ubiquitous, multifunctional protein that transports phospholipids between membrane surfaces and participates in cellular phospholipid metabolism during signal transduction and vesicular trafficking. We have determined the crystal structure of PITPalpha complexed with one molecule of phosphatidylcholine, a physiological ligands. We are using our structure to address questions of phospholipid specificity and membrane binding and lipid exchange to more throughly understand the role of PITP in cellular phospholipid metabolism.
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