LOOP MOVEMENT OF E COLI DIHYDROOROTASE

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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. Movements of structural domains of enzymes can be critical to their activity. Generally these domains have different conformations depending on the catalytic state of the enzyme. Therefore, the study of the structures of enzymes in conformational states is critical to understanding the enzyme catalysis and inhibitor design. Dihydroorotase (DHOase) is a zinc metalloenzyme that catalyzes the reversible cyclization of N-carbamyl-L- aspartate to L-dihydroorotate in the third step of de novo pyrimidine synthesis. In a recently determined structure of E. coli DHOase (Lee et al. (2005), J Mol Biol, 348, 523-533), we observed two different conformations of a loop comprised of residues 105-115. These conformations may be tightly linked to the catalytic state of DHOase. We have generated a series of site-directed mutants to probe the role of these moveme