Structural characterization of the copper site in galactose oxidase using X-ray absorption spectroscopy.
X-ray absorption spectroscopy has been used to characterize the local structural environment of the Cu ion in the reductively inactivated, oxidatively activated, and active+substrate oxidation state derivatives of galactose oxidase. In all three cases, the local environment of the Cu is best modeled by a single shell of low-Z (N or O) scatterers. This is generally consistent with the structure determined crystallographically, although the EXAFS bond lengths are slightly, but significantly, shorter than those found crystallographically. The best-fit average bond lengths are 1.97, 1.95, and 1.98 A for inactive, active, and active+substrate, respectively. The CuII ion in the active and inactive derivatives has an apparent coordination number of 4, consistent with the equatorial ligation seen crystallographically. The CuI ion in the reduced+substrate derivative appears to have either a lower coordination number or a significantly more distorted local environment. The observed CuI-(N/O) bond length favors a model where the Cu become 3-coordinate in the substrate-reduced complex.
Clark
K
K
Department of Chemistry, University of Michigan, Ann Arbor 48109-1055.
Penner-Hahn
J E
JE
Whittaker
M
M
Whittaker
J W
JW
D003300:Copper; D005692:Galactose Oxidase / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D010084:Oxidation-Reduction; D013057:Spectrum Analysis; D014965:X-Rays
D008024:Ligands; D003300:Copper; D005692:Galactose Oxidase