The Dinuclear Cu_A Center in Cytochrome c Oxidase and N_2O Reductase-- A Metal-Metal Bond in Biology?

摘要

Neighboring metal centers that cooperate functionally in proteins are bridged predominantly by O, N, or S donor lig-ands. In special cases (such as in, for example, deoxyhemo-cyanin. an oxygen transport protein of molluscs and arthropods that can bindO_2 side-on), the metal centers (here Cu') can be held without additional bridging at a "nonbonding" distance of d> 3.5 A by the protein framework. Recently a direct metal-metal bond in biology was postulated for the first time for the dinuclear Cu_A center in a water-soluble protein domain of the cytochrome c oxidase of Bacillus suhiilis; this proposal was based on the results of new EXAFS measurements (EXAFS = extended X-ray absorption fine structure) and their interpretation in comparison with results from a model compound.