Primary Citation of Related Structures: 1CHH, 1CHI, 1CHJ
PubMed Abstract:
A combination of structural, functional, and mutagenic experiments has been used to study the roles of the invariant Phe82 and highly conserved Leu85 residues in cytochrome c, especially with respect to the complexation interface with electron transfer partners and maintenance of the hydrophobic heme pocket ...
A combination of structural, functional, and mutagenic experiments has been used to study the roles of the invariant Phe82 and highly conserved Leu85 residues in cytochrome c, especially with respect to the complexation interface with electron transfer partners and maintenance of the hydrophobic heme pocket. Structural analyses show that the F82Y, L85A, and F82Y/L85A mutant proteins all retain the characteristic cytochrome c fold, but that conformational alterations are introduced in the direct vicinity of the mutation sites. In particular, the additional hydroxyl group of Tyr82 is in direct spatial conflict with the side chain of Leu85 in the F82Y mutant protein, leading to rotation of the side chain of Tyr82 out toward the protein surface. This strain is relieved in the F82Y/L85A mutant protein where the phenyl ring of Tyr82 is accommodated in a conformation comparable to that of the phenylalanine normally present at this location. In addition, the available space vacated by the replacement of Leu85 with an alanine allows for the inclusion of two new internal water molecules, one of which is bound to Tyr82 and the other to Arg13. In contrast, in the L85A mutant protein, no internal water molecules are observed in this exclusively hydrophobic pocket, which is partially filled by shifts in nearby side chains. Overall, the conformational changes observed result from the optimization of side chain packing to reflect the spatial requirements of new side chains, the minimization of both vacant internal space and the solvent exposure of hydrophobic groups, and the attainment of maximal hydrogen bonding between available polar groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Related Citations:
Oxidation State-Dependent Conformational Changes in Cytochrome C Berghuis, A.M., Brayer, G.D. (1992) J Mol Biol 223: 959
High-Resolution Refinement of Yeast Iso-1-Cytochrome C and Comparisons with Other Eukaryotic Cytochromes C Louie, G.V., Brayer, G.D. (1990) J Mol Biol 214: 527
A Polypeptide Chain-Refolding Event Occurs in the Gly82 Variant of Yeast Iso-1-Cytochrome C Louie, G.V., Brayer, G.D. (1989) J Mol Biol 210: 313
Crystallization of Yeast Iso-2-Cytochrome C Using a Novel Hair Seeding Technique Leung, C.J., Nall, B.T., Brayer, G.D. (1989) J Mol Biol 206: 783
Role of Phenylalanine-82 in Yeast Iso-1-Cytochrome C and Remote Conformational Changes Induced by a Serine Residue at This Position Louie, G.V., Pielak, G.J., Smith, M., Brayer, G.D. (1988) Biochemistry 27: 7870
Organizational Affiliation:
Department of Biochemistry, University of British Columbia, Vancouver, Canada.
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