The Role of Cytochrome b₅ Structural Domains in Interaction with Cytochromes P450

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G. V. Sergeev^*, A. A. Gilep, and S. A. Usanov

Institute of Bioorganic Chemistry, Academy of Sciences of Belarus, ul. Akademika Kuprevicha 5/2, 220141 Minsk, Belarus; fax: 375 (172) 63-7274; E-mail: gvserg@iboch.bas-net.by

^* To whom correspondence should be addressed.

Received November 8, 2013; Revision received December 27, 2013

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To understand the role of the structural elements of cytochrome b₅ in its interaction with cytochrome P450 and the catalysis performed by this heme protein, we carried out comparative structural and functional analysis of the two major mammalian forms of membrane-bound cytochrome b₅ – microsomal and mitochondrial, designed chimeric forms of the heme proteins in which the hydrophilic domain of one heme protein is replaced by the hydrophilic domain of another one, and investigated the effect of the highly purified native and chimeric heme proteins on the enzymatic activity of recombinant cytochromes P4503A4 and P45017A1 (CYP3A4 and CYP17A1). We show that the presence of a hydrophobic domain in the structure of cytochrome b₅ is necessary for its effective interaction with its redox partners, while the nature of the hydrophobic domain has no significant effect on the ability of cytochrome b₅ to stimulate the activity of cytochrome P450-catalyzed reactions. Thus, the functional properties of cytochrome b₅ are mainly determined by the structure of the heme-binding domain.

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KEY WORDS: microsomal cytochrome b₅, outer mitochondrial membrane cytochrome b₅, cytochrome P450, CYP3A4, CYP17A1

DOI: 10.1134/S0006297914050046

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