Specific cation binding site in mammalian cytochrome oxidase

FEBS Letters

Mkrtchyan, Hratchik M¹  Kirichenko, Anna¹  Konstantinov, Alexander¹  Vygodina, Tatiana¹ 

[1] A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Building `A', Moscow 119 899, Russia

关键词: Cytochrome c oxidase;    Proton channel;    Calcium binding;    Sodium ion;    COX;    cytochrome c oxidase;   

DOI  :  10.1016/S0014-5793(98)00117-3

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Calcium ion binds reversibly with cytochrome c oxidase from beef heart mitochondria (K _d∼2 μM) shifting α- and γ-absorption bands of heme a to the red. Two sodium ions compete with one Ca²⁺ for the binding site with an average dissociation constant ∼3.6 mM. The Ca²⁺-induced spectral shift of heme a is specific for mammalian cytochrome c oxidase and is not observed in bacterial or yeast aa ₃ oxidases although the Ca²⁺-binding site has been revealed in the bacterial enzyme [Ostermeier, C., Harrenga, A., Ermler, U. and Michel, H. (1997) Proc. Natl. Acad. Sci. USA 94, 10547–10553]. As His-59 and Gln-63 involved in Ca²⁺ binding with Subunit I of P. denitrificans oxidase are not conserved in bovine oxidase, these residues have to be substituted by alternative ligands in mammalian enzyme, which is indeed the case as shown by refined structure of bovine heart cytochrome oxidase (S. Yoshikawa, personal communication). We propose that it is interaction of Ca²⁺ with the species-specific ligand(s) in bovine oxidase that accounts for perturbation of heme a. The Ca²⁺/Na⁺-binding site may be functionally associated with the exit part of `pore B' proton channel in subunit I of mammalian cytochrome c oxidase.

【 授权许可】

Unknown