A possible mechanism for partitioning between homo- and heterodimerization of the yeast homeodomain proteins MATa1 and MATalpha2.
The yeast Saccharomyces cerevisiae has three cell types distinguished by the proteins encoded in their mating-type (MAT) loci: the a and alpha haploids, which express the DNA-binding proteins a1, and alpha1 and alpha2, respectively, and the a/alpha diploid which expresses both a1 and alpha2 proteins. In a/alpha cells, a1-alpha2 heterodimers repress haploid-specific genes and MATalpha1, whereas alpha2 homodimers repress a-specific genes, indicating dual regulatory functions for alpha2 in mating-type control. We previously demonstrated that the two leucine zipper-like coiled-coil motifs, called alpha2A and alpha2B, in the alpha2 N-terminal domain are important to a1-alpha2 heterodimerization. A unique feature of alpha2B is the occurrence of three atypical amino acid residues at a positions within the hydrophobic core. We have conducted mutational analyses of alpha2B peptides and the full-length protein. Our data suggest that these residues may play a critical role in partitioning of the alpha2 protein between heterodimerization with a1 and homodimerization with itself.
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Department of Biochemistry and Molecular Biology, Biotechnology Laboratory, and Protein Engineering Network of Centres of Excellence, University of British Columbia, Vancouver, Canada.
Smith
M
M
Houston
M E
ME
Adamson
J G
JG
Hodges
R S
RS
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D002942:Circular Dichroism; D019281:Dimerization; D018398:Homeodomain Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007532:Isoleucine; D008969:Molecular Sequence Data; D009154:Mutation; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D018398:Homeodomain Proteins; C096063:MATA1 protein, S cerevisiae; C062928:MATA2 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D007532:Isoleucine