Sequence hom ologies suggest that the PYP fold is the structural prototype for the superfamily of PAS domains found in diverse biological sensors and clock proteins. We used millisecond time-resolved Laue crystallography and simultaneous optical spectroscopy to determine the first atomic structure for a protein photocycle intermediate. The two PYP structures reveal the synergistic interactions between the chromophore and the protein that tune the spectral and kinetic properties of the light cycle for efficient protein-mediated signal transduction. Sulfite Reductase Hemoprotein Sulfite and nitrite reductases catalyze fundamental chemical transformations for biogeochemical cycling of sulfur and nitrogen. Coupled spectroscopy and crystal lography of the enzyme in three oxidation states showed that heme activation occurs via reduction-mediated ligand exchange.
T switch with concomitant release of oxygen .
Superoxide Dismutase For SOD metalloenzymes, we solved structures of bacterial, bovine, and human mutant enzymes to characterize the structural basis for their activity and stability. Structures of the oxi dized and reduced states of bovine SOD and active-site mutants of human SOD provide information on the enzyme's mechanism. Our bacterial SOD structure is representative of the class of SODs from bacterial pathogens and provides the potential for drug desi gn. Antibody Interactions Antibody interactions are a final focus for characterizing protein recognition, function, and interaction. With V. Roberts and S. Benkovic, we designed, constructed, and characterized metalloantibodies and catalytic antibodies that exploit the versatility of the sequence-variable, but structurally conserved antibody scaffold.