X-RAY-ABSORPTION SPECTROSCOPY OF PYROCOCCUS-FURIOSUS RUBREDOXIN

X-ray absorption spectroscopy has been used to probe the frozen soluti on structure of the metal site in Pyrococcus furiosus rubredoxin in th e native, iron-containing protein and in zinc- and mercury-substituted proteins, For all samples studied, the spectra have been interpreted in terms of a single shell of coordinated sulfur, with approximately t etrahedral coordination. For the native protein we obtain Fe-S bond-le ngths of 2.29 and 2.33 Angstrom for oxidized and reduced proteins, res pectively. These values are in excellent agreement with those previous ly obtained from X-ray crystallography. The metal-substituted rubredox ins possess metal-sulfur bond lengths of 2.34 and 2.54 Angstrom for th e zinc- and mercury-substituted proteins, respectively.