Yeast iso-1-cytochrome c: genetic analysis of structural requirements.
We describe the use of classical and molecular genetic techniques to investigate the folding, stability, and enzymatic requirements of iso-1-cytochrome c from the yeast Saccharomyces cerevisiae. Interpretation of the defects associated with an extensive series of altered forms of iso-1-cytochrome c was facilitated by the recently resolved three dimensional structure of iso-1-cytochrome c [(1987) J. Mol. Biol. 199, 295-314], and by comparison with the phylogenetic series of eukaryotic cytochromes c. Residue replacements that abolish iso-1-cytochrome c function appear to do so by affecting either heme attachment or protein stability; no replacements that abolish electron transfer function without affecting protein structure were uncovered. Most nonfunctional forms retained at least partial covalent attachment to the heme moiety; heme attachment was abolished only by replacements of Cys19 and Cys22, which are required for thioether linkage, and His23, a heme ligand. Replacements were uncovered that retain function at varying levels, including replacements at evolutionarily conserved positions, some of which were structurally and functionally indistinguishable from wild type iso-1-cytochrome c.
Hampsey
D M
DM
Department of Biophysics, University of Rochester Medical Center, NY 14642.
Das
G
G
Sherman
F
F
D000595:Amino Acid Sequence; D001483:Base Sequence; D003574:Cytochrome c Group / Q000235:genetics / Q000378:metabolism; D045304:Cytochromes c; D004579:Electron Transport; D005057:Eukaryotic Cells / Q000201:enzymology; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D006418:Heme / Q000378:metabolism; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D012689:Sequence Homology, Nucleic Acid; D013329:Structure-Activity Relationship
C014059:CYC1 protein, S cerevisiae; D003574:Cytochrome c Group; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D006418:Heme; D045304:Cytochromes c