Structural Studies of Metabolic Membrane Proteins

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DESCRIPTION (provided by applicant): We have obtained diffracting crystals of two membrane proteins involved in the glycerol metabolic pathway in bacteria, glycerol facilitator and glycerol-3-phosphate dehydrogenase. This is a significant step towards crystal structure determination and these structures will yield valuable new insight, linking protein folds to function and protein-protein interactions as well as mechanisms of catalysis, regulation, and transmembrane uptake of solute molecules. Underlying effective mechanisms of bacterial proliferation are means of mediating oxidative and carbohydrate metabolism. This structural study focuses on elucidating structure-function relationships of key bacterial membrane proteins that mediate fundamental oxidative and carbohydrate metabolism. We have been engaged in structural studies of these metabolic proteins for several years and are at pivotal point in integrating all of our results into a comprehensive and coherent picture of metabolism in these pathogenic bacteria. We have determined the structures of three other members of the oxidative and glycerol metabolism pathways, including NADH peroxidase, NADH oxidase, and glycerol kinase. This proposal addresses key questions correlating structure to function and regulation. Gly-3-phosphate dehydrogenase is of particular medical importance as it is a key player in providing triose phosphate intermediates for biosynthesis of polysaccharides that form biofilm and protects the bacterium from dehydration as well as antibiotic therapy. This membrane-protein structural study has the potential to yield new and novel results, which are not provided by high-throughput structural genomics. We have overcome some of the most difficult and rate-limiting hurdles in membrane protein structural studies by obtained diffracting crystals of the glycerol facilitator (2.4 A) from Gram-positive Streptococcus pneumonia, a membrane protein involved in glycerol uptake and likely to be regulated via protein-protein interactions with glycerol kinase, whose structure we've recently determined. Subtle but significant differences exist between this and the Gram-negative E. coli facilitator. We have diffracting crystals of the glycerol-3-phosphate dehydrogenase (3.3 A) from Pseudomonas aeruginosa and have promising indications for better diffracting crystals. Our specific aims are to obtain atomic resolution structures of both membrane proteins, both of which are likely to be novel targets for antibiotic design and therapy.