Oxidation-state-dependent protein docking between cytochrome c and cytochrome b5: High-pressure laser flash photolysis study

Yoshiaki Furukawa, Koichiro Ishimori, Isao Morishima

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Abstract

To characterize the protein-protein interaction during electron transfer, we used Zn-substituted cytochrome c (ZnCytc) as a model of ferrous Cytc and determined the volume change, ΔVd Zn, for the dissociation of its complex with ferric cytochrome b5 (Cytb5) by the pressure dependence of its photoinduced electron-transfer kinetics. Under ambient pressure, the dissociation constant, Kd Zn, of the ZnCytc/Cytb5 complex was dependent on the buffer concentration, 1.5 and 12 μM in 2 and 10 mM Tris-HCl, pH 7.4, respectively, which was consistent with formation of salt bridges in its complexation. The dissociation of one salt bridge is usually associated with large volume changes of -10 to -30 cm3 mol-1, while pressure dependence of Kd Zn resulted in smaller value of ΔVd Zn, -8.5 cm3 mol-1. Therefore, the interaction between ZnCytc and Cytb5 cannot be explained only by salt bridge interaction, and the partial cancellation by the positive volume change due to the additional hydrophobic interaction is a plausible explanation for the observed ΔVd Zn. In addition, ΔVd Zn of -8.5 cm3 mol-1 was considerably smaller than the previously reported volume change, ΔVd Fe, of -122 cm3 mol-1 in the ferric Cytc/Cytb5 complex dissociation [Rodgers and Sligar (1991) J. Mol. Biol. 221, 1453-1460]. ZnCytc used here has been assumed to be a reliable model of ferrous Cytc, and thus the discrepancy between our present ΔVd Zn and the previous ΔVd Fe is discussed on the basis of the protein docking dependent on the oxidation states of heme iron in Cytc.

Original languageEnglish
Pages (from-to)9824-9832
Number of pages9
JournalBiochemistry
Volume41
Issue number31
DOIs
Publication statusPublished - 2002 Aug 6
Externally publishedYes

Fingerprint

Cytochromes b5
Photolysis
Cytochromes c
Lasers
Pressure
Oxidation
Salts
Proteins
Electrons
Complexation
Heme
Hydrophobic and Hydrophilic Interactions
Buffers
Iron
Kinetics

ASJC Scopus subject areas

  • Biochemistry

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Oxidation-state-dependent protein docking between cytochrome c and cytochrome b5 : High-pressure laser flash photolysis study. / Furukawa, Yoshiaki; Ishimori, Koichiro; Morishima, Isao.

In: Biochemistry, Vol. 41, No. 31, 06.08.2002, p. 9824-9832.

Research output: Contribution to journalArticle

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