STRUCTURAL STUDIES ON PROTEINS THAT CONTROL APOPTOSIS, SULFUR ASSIMILATION & NEU

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Time is requested at SSRL for high-resolution structure determination of proteins from three different biological systems. One system involves viral proteins that inhibit apoptosis. In this proposal renewal, my laboratory is actively pursuing structure determination of complexes between the viral protein and the cellular caspases, which they inhibit. We recently have grown crystals both of the pre- and post-cleavage complex that diffract to 5 ¿ and 4.6 ¿ resolution respectively on beam line 9-1. We are currently pursuing experiments to increase the order in the crystals to improve diffraction. The second system involves proteins that assimilate inorganic sulfur from the environment into living organisms. We have recently determined the structure of the enzyme ATP sulfurylase, which catalyzes the first committed step in sulfur assimilation, from two different species. We will now be employing site-directed mutagenesis to create mutants to study structure-function relationships to understand the allosteric regulation as well as study these enzymes from human. The last system for which time is requested is on a PLP dependent enzyme gamma-aminobutyrate aminotransferase. This enzyme is an important target for neuroactive drugs used in treatment of epilepsy, Huntington's disease, schizophrenia and Alzheimer's disease. We have solved the E. coli enzyme structure and will study structural aspects of inhibition complexed with drugs and inhibitors. The high flux from SSRL will result in higher quality data at much higher resolution and enable better more detailed understanding for all the protein structures in these three systems.