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Major changes in copper coordination accompany reduction of peptidylglycine monooxygenase: implications for electron transfer and the catalytic mechanism

Authors :
Francis C. Rhames
Shulamit Jaron
Martina Ralle
Ninian J. Blackburn
Source :
JBIC Journal of Biological Inorganic Chemistry. 5:341-353
Publication Year :
2000
Publisher :
Springer Science and Business Media LLC, 2000.

Abstract

X-ray absorption spectroscopy has been used to probe the local coordination of the copper centers in the oxidized and reduced states of the peptidylglycine monooxygenase catalytic core (PHMcc) in both the resting and substrate-bound forms of the enzyme. The results indicate that reduction causes significant changes in coordination number and geometry of both Cu centers (CuH and CuM). The CuH center changes from 4- or 5-coordinate tetragonal to a 2-coordinate configuration, with one of the three histidine ligands becoming undetectable by EXAFS (suggesting that it has moved away from the CuH by at least 0.3 A). The CuM center changes from 4- or 5-coordinate tetragonal to a trigonal or tetrahedral configuration, with an estimated 0.3-0.5 A movement of the M314 S ligand. Reduction also leads to loss of coordinated water from both of the coppers. Substrate binding has little or no effect on the local environment of the Cu centers in either oxidation state. These findings bring into question whether direct electron transfer between CuH and CuM via a tunneling mechanism can be fast enough to support the observed catalytic rate, and suggest that some other mechanism for electron transfer, such as superoxide channeling, should be considered.

Details

ISSN :
14321327 and 09498257
Volume :
5
Database :
OpenAIRE
Journal :
JBIC Journal of Biological Inorganic Chemistry
Accession number :
edsair.doi.dedup.....9cccce8201d8c848f5d01bddd8f49b0d
Full Text :
https://doi.org/10.1007/pl00010663