Dramatic Thermostabilization of Yeast Iso-1-cytochrome c by an Asparagine → Isoleucine Replacement at Position 57

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 86; no. 2; pp. 496 - 499
• Main Authors: Das, Goutam, Hickey, David R., McLendon, Donna, McLendon, George, Sherman, Fred
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.01.1989; National Acad Sciences
• Subjects: Alleles; Amino Acid Sequence; Amino acids; Analytical, structural and metabolic biochemistry; Asparagine; Base Sequence; Biochemistry; Biological and medical sciences; Codons; Cytochrome c Group - genetics; Cytochromes c; DNA, Fungal - genetics; Free energy; Fundamental and applied biological sciences. Psychology; Genetic mutation; Hemoproteins; Hot Temperature; Isoleucine; Metalloproteins; Molecular Sequence Data; Mutation; Proteins; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae Proteins; Site directed mutagenesis; Thermal stability; Transition temperature; Yeasts; Fungi; Cytochrome c; Yeast; Molecular structure; Site directed mutagenesis; Ascomycetes; Structure function relationship; Saccharomyces cerevisiae; Thermal stability; Thallophyta
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.86.2.496

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 (Δ G degrees) for thermal unfolding.