Mutational hypersensitivity of a gene regulatory protein: Saccharomyces cerevisiae Gal80p.
The inhibitor of galactose catabolic (GAL) gene expression in Saccharomyces cerevisiae, Gal80p, interacts with the activator Gal4p and the signal transducer Gal3p and self-associates. Selection for loss of Gal80p inhibitor function yielded gal80 mutants at an extremely high rate. Out of these, 21 nonoverlapping point mutants were identified; each were due to a single-amino-acid exchange in conserved residues. Semiquantitative biochemical analysis of the corresponding mutant proteins revealed that each of the 21 amino acid alterations caused simultaneous defects in every single protein-protein interaction and in Gal80's structural integrity. Thus, Gal80 provides an unprecedented example for a protein's structural sensitivity to minimal sequence alterations.
Institute of Microbiology, Biocenter Niederursel, Goethe University, Frankfurt, Germany. k.melcher@ulster.ac.uk
Karsten
K
Melcher
D019943:Amino Acid Substitution / Q000235:genetics*; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D015723:Gene Library; D005818:Genetic Engineering; D017354:Point Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000378:metabolism
D004268:DNA-Binding Proteins; C052130:GAL4 protein, S cerevisiae; C055002:GAL80 protein, S cerevisiae; C099289:Gal3 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors