Crystal structure and spectroscopic studies of a stable mixed-valent state of the hemerythrin-like domain of a bacterial chemotaxis protein

Akira Onoda, Yasunori Okamoto, Hiroshi Sugimoto, Yoshitsugu Shiro, Takashi Hayashi

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

The bacterial chemotaxis protein of Desulfovibrio vulgaris DcrH (DcrH-Hr) functions as an O2-sensing protein. This protein has a hemerythrin-like domain that includes a nonheme diiron center analogous to the diiron center of the hemerythrin (Hr) family. Interestingly, the O2 affinity of DcrHHr is 3.3 × 106 M-1, a value 25-fold higher than that of the Pectinaria gouldii Hr. This high affinity arises from the fast association of the O2 ligand with DcrH-Hr (kon = 5.3 × 10 8 M-1 s-1), which is made possible by a hydrophobic tunnel that accelerates the passage of the O2 ligand to the diiron site. Furthermore, the autoxidation kinetics indicate that the rate of autoxidation of DcrH-Hr is 54-fold higher than that of P. gouldii Hr, indicating that the oxy form of DcrH-Hr is not stable toward autoxidation. More importantly, a mixed-valent state, semimetR, which was spectroscopically observed in previous Hr studies, was found to be stable for over 1 week and isolable in the case of DcrH-Hr. The high-resolution crystal structures of the semimetR- (1.8 Å) and met-DcrH-Hr (1.4 Å) indicate that the semimetR- and met- DcrH-Hr species have very similar coordination geometry at the diiron site.

Original languageEnglish
Pages (from-to)4892-4899
Number of pages8
JournalInorganic chemistry
Volume50
Issue number11
DOIs
Publication statusPublished - 2011 Jun 6
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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