Cappellaro C, Baldermann C, Rachel R, Tanner W
Lehrstuhl für Zellbiologie und Pflanzenphysiologie, Universität Regensburg, Germany.
EMBO J. 1994 Oct 17;13(20):4737-44. doi: 10.1002/j.1460-2075.1994.tb06799.x.
Mating type-specific agglutination of Saccharomyces cerevisiae a and alpha cells depends on the heterophilic interaction of two cell surface glycoproteins, the gene products of AG alpha 1 and AGA2. Evidence is presented with immunogold labelling that the alpha-agglutinin is part of the outer fimbrial cell wall coat. The a-agglutinin is bound via two S-S bridges (Cys7 and Cys50) to a cell wall component, most probably the gene product of AGA1. His273 of alpha-agglutinin has previously been shown to be essential for a- and alpha-agglutinin interaction and a model based on two opposing ion-pairs had been proposed. By site-directed mutagenesis this possibility has now been excluded. With the help of various peptides, either chemically synthesized, obtained by proteolysis of intact glycosylated a-agglutinin or prepared from a fusion protein expressed in Escherichia coli, the biologically active region of a-agglutinin was located at the C-terminus of the molecule. A peptide consisting of the C-terminal 10 amino acids (GSPIN-TQYVF) was active in nanomolar concentrations. Saccharide moieties, therefore, are not essential for the mating type-specific cell-cell interaction; glycosylated peptides are, however, four to five times more active than non-glycosylated ones. Comparisons of the recognition sequences of the S. cerevisiae agglutinins with that of the Dictyostelium contact site A glycoprotein (gp80), as well as with those of the various families of cell adhesion molecules of higher eucaryotes, have been made and are discussed.
酿酒酵母a型和α型细胞的交配型特异性凝集取决于两种细胞表面糖蛋白（AGα1和AGA2的基因产物）的异嗜性相互作用。免疫金标记提供的证据表明，α-凝集素是外纤维状细胞壁外层的一部分。a-凝集素通过两个S-S桥（Cys7和Cys50）与一种细胞壁成分结合，很可能是AGA1的基因产物。先前已证明α-凝集素的His273对于a-凝集素和α-凝集素的相互作用至关重要，并提出了基于两个相反离子对的模型。现在通过定点诱变排除了这种可能性。借助化学合成的、通过完整糖基化a-凝集素的蛋白水解获得的或由大肠杆菌中表达的融合蛋白制备的各种肽，确定了a-凝集素的生物活性区域位于分子的C末端。由C末端10个氨基酸（GSPIN-TQYVF）组成的肽在纳摩尔浓度下具有活性。因此，糖基部分对于交配型特异性细胞间相互作用不是必需的；然而，糖基化肽的活性是非糖基化肽的四到五倍。已对酿酒酵母凝集素与盘基网柄菌接触位点A糖蛋白（gp80）以及高等真核生物各种细胞粘附分子家族的识别序列进行了比较并进行了讨论。
