This proposal requests funds for the purchase of an electronic area detector diffractometer for use in x-ray crystallographic studies of protein structures. It is an updated version of the proposal originally submitted Dec. 9, 1986. Proteins currently being investigated include a variety of complexes and mutants of E. coli, chicken and human dihydrofolate reductase, and mutants and complexes of yeast cytochrome c peroxidase. Additionally, crystals of two proteins relevant to DNA replication and repair have been crystallized and are being studied to establish their suitability for structure determination: repA1 of an E. coli plasmid and rat B-ploymerase. Still other proteins are undergoing crystallization trials. Acquisition of an area detector diffractometer will allow the PIs to collect data when crystals are ready for mounting and eliminate the need to wait, often several months, for access to a diffractometer in another laboratory; enhance the rate and flexibility of data collection; permit complete data sets to be collected from a minimum number of crystals; and provide accurate high-resolution data for structure refinement.
