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The nature of haem a3 in the oxidized state of cytochrome c oxidase. Evidence from low-temperature magnetic-circular-dichroism spectroscopy in the near infrared region.


ABSTRACT: The magnetic-circular-dichroism (m.c.d.) spectra of oxidized 'resting' bovine cytochrome c oxidase and the cyanide-inhibited form are reported at 5.15 T and at 4.2 K along with m.c.d. magnetization curves plotted at selected wavelengths. In both spectra there are features at 790nm and 1564nm due to Cua and haem a respectively, the e.p.r.-detectable components of the enzyme. There is a new peak at 1946nm only in the spectrum of the cyanide-inhibited enzyme. Arguments are advanced that assign this to low-spin ferric haem a3 bridged to Cua3, thereby forming a ferromagnetically coupled pair of metal ions.

SUBMITTER: Thomson AJ 

PROVIDER: S-EPMC1153838 | BioStudies | 1982-01-01

SECONDARY ACCESSION(S): 10.1042/bj2070167

REPOSITORIES: biostudies

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