NI ENZYME EXAFS BEYOND THE CU EDGE

点击翻译按钮获取中文摘要

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. Ni-Fe Hydrogenase in Desulfovibrio gigas catalyzes the reversible oxidation of molecular hydrogen at an unusual Ni-Fe cluster. The crystal structures for the inactive form A enzyme reveal a Ni ligated by two terminal cysteine sulfurs, as well as two cysteine sulfurs that bridge to an Fe(CO)(CN)2 unit, with a Ni-Fe distance of 2.95 ¿¿ An additional bridging light atom is also seen in this form (assigned as "oxygen"). The bridging atom appears absent in structures of the reduced and active forms of related hydrogenases. A precise understanding of the interatomic distances at the Ni-Fe center is important for an understanding of the catalytic mechanism. However, there is not complete agreement between EXAFS analyses, X-ray structures, and theoretical calculations on the structure of the Ni-Fe site. The controversies on the structure of Ni-Fe site in hydrogenase has raised our interest to reexamine the Ni site by Ni EXAF