Sen M, Marsh L
Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461.
J Biol Chem. 1994 Jan 14;269(2):968-73.
The Saccharomyces cerevisiae alpha-factor receptor has a 3400-fold higher affinity for the S. cerevisiae alpha-factor peptide (c-alpha-f) than for the Saccharomyces kluyveri alpha-factor peptide (k-alpha-f) as determined by competition for [3H] c-alpha-f binding. The S. kluyveri alpha-factor receptor has an approximately 2-fold higher affinity for k-alpha-f than for c-alpha-f. The S. kluyveri receptor gene (k-STE2) is incompletely regulated by S. cerevisiae mating type and poorly expressed on the surface of an S. cerevisiae mating type a strain. A chimeric receptor (c/k1) with amino acid residues 1-45 derived from S. cerevisiae and amino acid residues 46-427 from S. kluyveri exhibits the binding specificity of the S. kluyveri receptor. However, chimeric receptors containing residues 1-168 (c/k2) or 1-250 (c/k3) from S. cerevisiae and the remainder from the S. kluyveri receptor exhibit specificities similar to one another, but intermediate between the parent S. cerevisiae and S. kluyveri receptors. The relative ability of c-alpha-f and k-alpha-f to induce growth arrest in strains expressing chimeric receptors parallels relative affinity. Thus, two noncontiguous domains that include putative extracellular loops 1 and 3 and associated transmembrane segments, but exclude the extracellular NH2 terminus and loop 2, appear to contribute to alpha-factor receptor ligand specificity. COOH-terminal regions of the S. kluyveri receptor appear to confer a desensitization defect when expressed in S. cerevisiae. The S. cerevisiae receptor truncated at residue 296 retains ligand specificity for growth arrest.
通过[3H] c-α因子结合竞争测定，酿酒酵母α因子受体对酿酒酵母α因子肽（c-α-f）的亲和力比对克鲁维酵母α因子肽（k-α-f）高3400倍。克鲁维酵母α因子受体对k-α-f的亲和力比对c-α-f高约2倍。克鲁维酵母受体基因（k-STE2）受酿酒酵母交配型的调控不完全，在酿酒酵母交配型a菌株表面表达不佳。一种嵌合受体（c/k1），其1 - 45位氨基酸残基来自酿酒酵母，46 - 427位氨基酸残基来自克鲁维酵母，表现出克鲁维酵母受体的结合特异性。然而，含有酿酒酵母1 - 168位残基（c/k2）或1 - 250位残基（c/k3）以及其余来自克鲁维酵母受体的嵌合受体表现出彼此相似的特异性，但介于亲本酿酒酵母和克鲁维酵母受体之间。c-α-f和k-α-f在表达嵌合受体的菌株中诱导生长停滞的相对能力与相对亲和力平行。因此，两个不连续的结构域，包括假定的细胞外环1和3以及相关的跨膜片段，但不包括细胞外NH2末端和环2，似乎有助于α因子受体配体特异性。当在酿酒酵母中表达时，克鲁维酵母受体的COOH末端区域似乎导致脱敏缺陷。在296位残基处截断的酿酒酵母受体保留了对生长停滞的配体特异性。
