Mechanisms of autoxidation of the oxygen sensor FixL and Aplysia myoglobin: Implications for oxygen-binding heme proteins

Gonzalo Gonzalez, Marie A. Gilles-Gonzalez, Elena V. Rybak-Akimova, Maria Buchalova, Daryle H. Busch

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

On exposure to oxygen, ferrous heme is thought to autoxidize via three distinct mechanisms: (i) dissociation of protonated superoxide from oxyheme; (ii) reaction between a noncoordinated oxygen molecule and pentacoordinate deoxyheme, and (iii) reaction between a noncoordinated oxygen molecule and an intermediate having water coordinated to the ferrous heme iron. The formation of a hexacoordinate aquomet (H2O·Fe3+) species has been proposed to drive mechanism (iii); consequently, heme proteins with a pentacoordinate met (Fe3+) form might be expected to lack this pathway. We have measured the dependence of autoxidation rate on oxygen concentration for Rhizobium meliloti FixL and Aplysia kurodai myoglobin, which have pentacoordinate met forms. For both proteins, the bell shape of this dependence shows that they autoxidize primarily by mechanism (iii), indicating that a hexacoordinate aquomet species is not required for this mechanism. A novel presentation of the oxygen dependence of autoxidation rates that uses heme saturation, rather than oxygen concentration, more clearly reveals the relative contributions of autoxidation pathways.

Original languageEnglish (US)
Pages (from-to)10188-10194
Number of pages7
JournalBiochemistry
Volume37
Issue number28
DOIs
StatePublished - Jul 14 1998

ASJC Scopus subject areas

  • Biochemistry

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