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Heterodimerization of the yeast MATa1 and MAT alpha 2 proteins is mediated by two leucine zipper‐like coiled‐coil motifs.
Author(s) -
Ho C.Y.,
Adamson J.G.,
Hodges R.S.,
Smith M.
Publication year - 1994
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1994.tb06394.x
Subject(s) - columbia university , leucine zipper , biology , library science , genetics , sociology , media studies , computer science , gene , peptide sequence
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 alpha 1 and alpha 2, respectively, and the a/alpha diploid which expresses both a1 and alpha 2 proteins. In a/alpha cells, a1‐alpha 2 heterodimers repress haploid‐specific genes, while alpha 2 homodimers repress a‐specific genes, indicating a dual regulatory function for alpha 2 in mating type control. a1 does not form homodimers. We have identified two sequences in the alpha 2 N‐terminal domain which contain the 3,4‐hydrophobic heptad repeat pattern characteristic of coiled‐coils. Mutational analyses show that both sequences are important to a1‐alpha 2 heterodimerization. We propose that these two sequences associate in a coiled‐coil‐like manner with a sequence within a1 which bears two adjacent, overlapping 3,4‐hydrophobic heptad repeats. This model, which describes a novel dimerization motif for homeodomain proteins, also provides a mechanism by which a1‐a1 homodimerization is prevented.