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UV resonance Raman scattering from metal‐coordinating histidine residues in Cu,Zn‐superoxide dismutase
Author(s) -
Hashimoto Shinji,
Ono Kunio,
Takeuchi Hideo
Publication year - 1998
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/(sici)1097-4555(199810/11)29:10/11<969::aid-jrs328>3.0.co;2-6
Subject(s) - raman spectroscopy , imidazole , chemistry , imidazolate , resonance raman spectroscopy , metal , resonance (particle physics) , histidine , protonation , ring (chemistry) , crystallography , raman scattering , metal ions in aqueous solution , stereochemistry , ion , inorganic chemistry , enzyme , organic chemistry , physics , particle physics , optics
Metal‐binding modes of histidine residues in Cu,Zn‐superoxidedismutase (Cu,Zn‐SOD) were investigated by UV resonance Ramanspectroscopy. The metal‐bridging imidazolate (Im ‐ ) ring ofHis61 gives prominent Raman bands at ca . 1565, 1335, 1285,1260, 1050 and 980 cm ‐1 . On the other hand, the imidazolering of other histidines gives a Raman band at ca . 1395 or 1355cm ‐1 when it is ligated to a metal ion via theN τ or N π atom, respectively, and theother nitrogen atom is deuterated (ImD). These Raman marker bandstogether with the previously established correlation between theC 4 =C 5 stretching wavenumber andmetal‐coordination site for non‐deuterated imidazole (ImH) were usedto investigate the metal‐binding modes of histidine residues in thereduced and inhibitor‐bound states of Cu,Zn‐SOD. Upon reduction of theenzyme, the Raman bands of the metal‐bridging Im ‐ ringdisappear. Concomitantly, a new band appears at 1590 cm ‐1 ,which is assignable to the C 4 =C 5 stretchof an ImH ring coordinating to a metal ion via the N π atom. These Raman spectral changes provide direct evidence that theCu—N τ linkage of His61 is broken upon reductionand the N τ atom is protonated in the reduced state. Thebinding of a competitive inhibitor (CN ‐ ) produceswavenumber downshifts of Raman bands arising from vibrations of theN τ —C 5 =C 4 moiety ofthe His61 Im ‐ ring, indicating a structural modification ofHis61 by the inhibitor binding. © 1998 John Wiley & Sons,Ltd.