title: The role of cysteine residues in the homeodomain protein Mat alpha 2 in mating-type control of Saccharomyces cerevisiae.
abstract: The Mat alpha 2 homeodomain protein plays a pivotal role in the control of cell type in Saccharomyces cerevisiae. The homeodomain in the C-terminal region of Mat alpha 2 functions as a DNA-binding domain and the N-terminal region, containing two cysteine residues at positions 33 and 34, is thought to be involved in formation of Mat alpha 2 homodimers via disulfide bonds. mat alpha 2 mutants, isolated in a previous study, in which haploid-specific genes cannot be repressed by the Matal-Mat alpha 2 heterodimer but a-specific genes can be repressed by the Mat alpha 2 homodimer, were found to produce mutant Mat alpha 2 with a substitution of tyrosine or phenylalanine for Cys33. To clarify the role of Cys33 and Cys34 in the Mat alpha 2 protein, we generated several mat alpha 2 mutants by site-directed mutagenesis which had serine residues in place of these Cys residues. Transforming MATa cells with plasmids carrying these mat alpha 2 (MAT alpha 1+) mutations rendered transformants unable to mate. Northern blot analysis revealed that transcription of the a-specific gene STE2 and the haploid-specific locus RME1 in these transformants is repressed to the same level as in wild-type MATa/MAT alpha cells. We concluded that neither Cys33 nor Cys34 is required for repression of a-specific genes by the Mat alpha 2 homodimer or of haploid-specific genes by the Matal-Mat alpha 2 heterodimer, and therefore suggest that Mat alpha 2 homodimer formation in vivo is not mediated by disulfide linkage.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Mukai
authors.forename: Y
authors.initials: Y
authors.lastname: Ohno-Yamashita
authors.forename: Y
authors.initials: Y
authors.lastname: Oshima
authors.forename: S
authors.initials: S
authors.lastname: Harashima
mesh_terms: D003545:Cysteine / Q000235:genetics*; D019281:Dimerization; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D012694:Serine / Q000235:genetics; D013440:Sulfides; D014157:Transcription Factors; D014170:Transformation, Genetic; D014443:Tyrosine / Q000235:genetics
chemical_list: D005656:Fungal Proteins; D018398:Homeodomain Proteins; C062928:MATA2 protein, S cerevisiae; C071594:RME1 protein, S cerevisiae; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D013440:Sulfides; D014157:Transcription Factors; D014443:Tyrosine; D012694:Serine; D003545:Cysteine