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Title
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Role of phenylalanine-82 in yeast iso-1-cytochrome c and remote conformational changes induced by a serine residue at this position.
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Authors
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G.V.Louie,
G.J.Pielak,
M.Smith,
G.D.Brayer.
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Ref.
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Biochemistry, 1988,
27,
7870-7876.
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PubMed id
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Abstract
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A three-dimensional structural analysis of the reduced form of the Ser-82 mutant
protein of yeast iso-1-cytochrome c has been completed to 2.8-A resolution.
Replacement of Phe-82 with a serine residue results in conformational changes
both near and remote from the mutation site. Those groups undergoing positional
shifts near Ser-82 include Arg-13, Gly-83 and -84, and the CBB methyl of the
heme group. Remote shifts are centered about the propionate of pyrrole ring A
and principally involve Asn-52, Trp-59, and an internally buried water molecule,
WAT-166. Placement of a serine side chain at position 82 also leads to the
formation of a large solvent channel which substantially increases the solvent
accessibility of the heme group. This would appear to account for the much lower
reduction potential observed for this protein. The detrimental effect of Ser-82
on both the steady-state activity and the rate of electron transfer in
complexation with cytochrome c peroxidase can also be interpreted in terms of
the modified character of the region about the mutation site. The remote
conformational changes observed appear to represent the equivalent of the
initial conformational changes occurring as yeast iso-1-cytochrome c is
converted to the fully oxidized state during an electron-transfer event. These
results agree well with the proposal [Moore, G. R. (1983) FEBS Lett. 161,
171-175] that the trigger for conformational changes between oxidation states
resides in the nature of the interactions between the heme iron atom and the
pyrrole ring A propionate group.
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