Dramatic thermostabilization of yeast iso-1-cytochrome c by an asparagine----isoleucine replacement at position 57.
Two Saccharomyces cerevisiae yeast mutants, cyc1-73 and cyc1-190, contain nonfunctional and presumably unstable forms of iso-1-cytochrome c due to Gly-34----Ser and His-38----Pro replacements, respectively. Second-site reversions that produced Asn-57----Ile replacements at least partially restored function, presumably by alleviating the instability of these two altered iso-1-cytochromes c. Introduction of the Ile-57 replacement by site-directed mutagenesis in an otherwise normal protein resulted in a 17 degrees C increase in the transition temperature (Tm), corresponding to over a 2-fold increase in the free energy change (delta G degrees) for thermal unfolding.
Das
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Department of Biochemistry, University of Rochester, NY 14642.
Hickey
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McLendon
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McLendon
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Sherman
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D000595:Amino Acid Sequence; D001216:Asparagine; D001483:Base Sequence; D003574:Cytochrome c Group / Q000235:genetics*; D045304:Cytochromes c; D004271:DNA, Fungal / Q000235:genetics; D006358:Hot Temperature; D007532:Isoleucine; D008969:Molecular Sequence Data; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins
C014059:CYC1 protein, S cerevisiae; D003574:Cytochrome c Group; D004271:DNA, Fungal; D029701:Saccharomyces cerevisiae Proteins; D007532:Isoleucine; D001216:Asparagine; D045304:Cytochromes c