MISC

2004年4月

Catalytic and structural role of a metal-free histidine residue in bovine Cu-Zn superoxide dismutase

BIOCHEMISTRY
  • A Toyama
  • ,
  • Y Takahashi
  • ,
  • H Takeuchi

43
16
開始ページ
4670
終了ページ
4679
記述言語
英語
掲載種別
DOI
10.1021/bi049767k
出版者・発行元
AMER CHEMICAL SOC

Cu-Zn superoxide dismutase (SOD) contains a conserved, metal-free His residue at an opening of the backbone beta-barrel in addition to six Cu- and/or Zn-bound His residues in the active site. We examined the protonation and hydrogen bonding state of the metal-free His residue (His41) in bovine SOD by UV Raman spectroscopy. Analysis of the His Raman intensity at 1406 cm(-1) in a D2O solution has shown that His41. has a pK(a) of 9.4, consistent with the NMR and X-ray structures at acidic to neutral pH, in which two imidazole nitrogen atoms of cationic His41 are hydrogen bonded to the main chain C=O groups of Thr37 and His118. Upon deprotonation of His41 at pH 9.4, the Thr37-His41-His118 hydrogen bond bridge breaks on the His118 side and SOD loses 70% of its activity. Concomitantly, hydrogen-deuterium exchange is accelerated for amide groups of beta-strands, indicating an increased conformational fluctuation of the beta-barrel. Thr37 and His41 are in direct contact with Leu36, whose hydrophobic side chain closes off the opening of the beta-barrel, while His118 is indirectly connected to Arg141 that assists the docking of superoxide to Cu. These Raman findings strongly suggest that the His41-mediated hydrogen bond bridge plays a crucial role in keeping the protein structure suitable for highly efficient catalytic reactions. The catalytic and structural role of His41 is consistent with the observation that the mutation of His43 in human SOD (equivalent to His41 in bovine SOD) to Arg largely reduces the dismutase activity and the protein structural stability.

Web of Science ® 被引用回数 : 20

リンク情報
DOI
https://doi.org/10.1021/bi049767k
CiNii Articles
http://ci.nii.ac.jp/naid/80016662161
PubMed
https://www.ncbi.nlm.nih.gov/pubmed/15096035
Web of Science
https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000220967900005&DestApp=WOS_CPL

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