JBIC Journal of Biological Inorganic Chemistry

, Volume 22, Issue 5, pp 705–712

Effect of methionine80 heme coordination on domain swapping of cytochrome c

  • Shun Hirota
  • Nobuhiro Yamashiro
  • Zhonghua Wang
  • Satoshi Nagao
Original Paper

DOI: 10.1007/s00775-017-1446-3

Cite this article as:
Hirota, S., Yamashiro, N., Wang, Z. et al. J Biol Inorg Chem (2017) 22: 705. doi:10.1007/s00775-017-1446-3
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Part of the following topical collections:
  1. AsBIC8: 8th Asian Biological Inorganic Chemistry Special Issue

Abstract

Cytochrome c (cyt c) forms oligomers by domain swapping. It exchanges the C-terminal α-helical region between protomers, and the Met80‒heme iron bond is perturbed significantly in domain-swapped oligomers. The peroxidase activity of cyt c increases by Met80 dissociation from the heme iron, which may trigger apoptosis. This study elucidates the effect of the Met80 heme coordination on cyt c domain swapping by obtaining oligomers for both wild-type (WT) and M80A human cyt c by an addition of ethanol to their monomers, followed by lyophilization and dissolution to buffer, and investigating their dimer properties. The absorption and circular dichroism spectra of WT and M80A cyt c exhibited similar changes upon dimerization, indicating that Met80 does not affect the oligomerization process significantly. According to differential scanning calorimetric measurements, Met80 coordination to the heme iron had an effect on the stabilization of the monomer (ΔH = 16 kcal/mol), whereas no large difference was observed between the dimer-to-monomer dissociation temperatures of WT and M80A cyt c (61.0 °C). The activation enthalpy values were similar and relatively large for the dissociation of both WT and M80A cyt c dimers (WT, 120 ± 10 kcal/mol; M80A, 110 ± 10 kcal/mol), indicating that the dimers suffered large structural changes upon dissociation to monomers independent of the Met80 coordination to the heme iron. These results indicate that cyt c domain swapping may occur regardless of the Met80 coordination, whereas the monomer is stabilized by Met80 but the domain-swapped dimer structure and stability are less affected by the Met80 coordination.

Keywords

Cytochrome c Domain swapping Methionine coordination Oligomerization 

Abbreviations

CD

Circular dichroism

Cyt

Cytochrome

DSC

Differential scanning calorimetry

FPLC

Fast protein liquid chromatography

HT

Hydrogenobacter thermophilus

ΔH

Enthalpy change

ΔH

Activation enthalpy

PA

Pseudomonas aeruginosa

K

Rate constant

ΔS

Activation entropy

SEC

Size exclusion chromatography

Tm

Dissociation temperature

WT

Wild-type

Supplementary material

775_2017_1446_MOESM1_ESM.pdf (203 kb)
Supplementary material 1 (PDF 204 kb)

Funding information

Funder NameGrant NumberFunding Note
Japan Society for the Promotion of Science
  • JP15K13744
  • JP16H00839
  • JP16K17935
  • JP26288080

Copyright information

© SBIC 2017

Authors and Affiliations

  • Shun Hirota
    • 1
  • Nobuhiro Yamashiro
    • 1
  • Zhonghua Wang
    • 1
    • 2
  • Satoshi Nagao
    • 1
  1. 1.Graduate School of Materials ScienceNara Institute of Science and TechnologyIkomaJapan
  2. 2.College of Chemistry and Chemical EngineeringChina West Normal UniversityNanchongChina

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