This project seeks to expand upon our knowledge of the structure, function and chemical reactivity of biological iron- sulfur (FeS) clusters, the most ubiquitous electron carriers in nature. Dr. Adams is investigating the structure and properties of a new type of FeS center, termed the H cluster, found at the catalytic site of hydrogenase. This enzyme has the unique ability to catalyze H2 oxidation and H2 production, reactions of fundamental chemical and biological significance. In two hydrogenases from the anaerobic bacterium, Clostridium pasteurianum, he has shown that the novel H cluster is comprised of four to six Fe atoms and has two nitrogenous ligands, one of which is displaced when the cluster covalently binds CO, a potent inhibitor. Further potentiometric, spectroscopic and crystallographic analyses of these enzymes are proposed. He will also investigate the biochemical and spectroscopic properties of an extremely thermophilic version of the H cluster in a tungsten-dependent FeS-Hydrogenase that has been purified from Thermotoga maritima, a unique eubacterium that grows at 90C. He has show that spectroscopic properties similar to those of the hydrogenase H cluster are exhibited by the novel FeS cluster of an exceptionally thermostable Ferredoxin from Pyrococcus furiosus, an archaebacterium that grows optimally at 100C. Further modification of this FeS center will be explored as a potential model for the H2-activating H cluster of the hydrogenases.
