An investigation into a cardiolipin acyl chain insertion site in cytochrome c
Mitochondrial cytochrome c associates with the phosphoplipid cardiolipin (CL) through a combination of electrostatic and hydrophobic interactions. The latter occurs by insertion into cytochrome c of an acyl chain, resulting in the dissociation of the axial Met-80 heme-iron ligand. The resulting five...
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Published in | Biochimica et biophysica acta Vol. 1817; no. 5; pp. 780 - 791 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
Netherlands
Elsevier B.V
01.05.2012
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Subjects | |
Online Access | Get full text |
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Summary: | Mitochondrial cytochrome c associates with the phosphoplipid cardiolipin (CL) through a combination of electrostatic and hydrophobic interactions. The latter occurs by insertion into cytochrome c of an acyl chain, resulting in the dissociation of the axial Met-80 heme-iron ligand. The resulting five coordinate cytochrome c/CL complex has peroxidatic properties leading to peroxidation of CL and dissociation of the complex. These events are considered to be pre-apoptotic and culminate with release of cytochrome c from the mitochondria into the cytoplasm. Two distinct surface regions on cytochrome c have been suggested to mediate CL acyl chain insertion and this study has probed one of these regions. We have constructed a series of alanine mutants aimed at disrupting a surface cleft formed between residues 67–71 and 82–85. The physicochemical properties, peroxidase activity, CL binding, and kinetics of carbon monoxide (CO) binding to the ferrous cytochrome c/CL complex have been assessed for the individual mutants. Our findings reveal that the majority of mutants are capable of binding CL in the same apparent stoichiometry as the wild-type protein, with the extent to which the Met-80 ligand is bound in the ferrous cytochrome c/CL complex being mutant specific at neutral pH. Mutation of the species conserved Arg-91 residue, that anchors the cleft, results in the greatest changes to physicochemical properties of the protein leading to a change in the CL binding ratio required to effect structural changes and to the ligand-exchange properties of the ferrous cytochrome c/CL complex.
► A putative cardiolipin insertion site on mitochondrial cytochrome c has been studied. ► A series of alanine mutations in cytochrome c have been constructed. ► Cardiolipin interaction has been assessed using carbon monoxide as a small ligand probe. ► The alanine mutations influence the extent of CO binding in the ferrous cytochrome c complex. ► Arg-91 alters the cardiolipin binding stoichiometry. |
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Bibliography: | http://dx.doi.org/10.1016/j.bbabio.2012.02.010 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0005-2728 0006-3002 1879-2650 |
DOI: | 10.1016/j.bbabio.2012.02.010 |