Marsh L, Herskowitz I
Department of Biochemistry and Biophysics, University of California, San Francisco 94143.
Proc Natl Acad Sci U S A. 1988 Jun;85(11):3855-9. doi: 10.1073/pnas.85.11.3855.
We have cloned the gene for the alpha-factor receptor of the yeast Saccharomyces kluyveri by using the Saccharomyces cerevisiae receptor gene (c-STE2) as a probe. The nucleotide sequence of the S. kluyveri gene (k-STE2) shows that its predicted polypeptide contains seven hydrophobic segments capable of spanning a lipid bilayer and thus that, like c-STE2, it appears to be a member of the rhodopsin/beta-adrenergic receptor family. The k-STE2 polypeptide is 50% identical to that coded by c-STE2, with high conservation (greater than 67%) in the putative membrane-spanning domains. The carboxyl-terminal amino acid sequences are not similar, but both are very hydrophilic and rich in serine and threonine residues. The k-STE2 gene is functional in S. cerevisiae: it reverses the mating defect of an S. cerevisiae mutant defective in its STE2 gene. S. cerevisiae strains expressing k-STE2 rather than c-STE2 exhibit the mating-factor selectivity characteristic of S. kluyveri: better response to S. kluyveri alpha factor than to S. cerevisiae alpha factor. (S. cerevisiae normally responds much better to its own alpha-factor peptide than to the related alpha-factor peptide of S. kluyveri.) This observation demonstrates that the STE2 gene is responsible for ligand selectivity and provides additional evidence that the STE2 protein is the receptor for alpha factor.
我们利用酿酒酵母受体基因（c-STE2）作为探针，克隆了克鲁维酵母α因子受体基因。克鲁维酵母基因（k-STE2）的核苷酸序列表明，其预测的多肽含有七个能够跨越脂质双层的疏水片段，因此，与c-STE2一样，它似乎是视紫红质/β-肾上腺素能受体家族的成员。k-STE2多肽与c-STE2编码的多肽有50%的同一性，在假定的跨膜结构域中具有高度保守性（大于67%）。羧基末端氨基酸序列不相似，但两者都非常亲水，富含丝氨酸和苏氨酸残基。k-STE2基因在酿酒酵母中具有功能：它能逆转酿酒酵母中STE2基因缺陷的突变体的交配缺陷。表达k-STE2而非c-STE2的酿酒酵母菌株表现出克鲁维酵母的交配因子选择性特征：对克鲁维酵母α因子的反应比对酿酒酵母α因子的反应更好。（酿酒酵母通常对其自身的α因子肽的反应比对克鲁维酵母相关α因子肽的反应要好得多。）这一观察结果表明，STE2基因负责配体选择性，并提供了额外的证据表明STE2蛋白是α因子的受体。
