Molecular Complementarity of Yeast Glycoprotein Mating Factors

Abstract

Cell fusion between opposite mating types 5 and 21 of the yeast Hansenula wingei is initiated by a strong sexual agglutination reaction. The mating factors responsible for the specificity of cellular recognition are complementary glycoproteins which form a physical complex in vitro. The complex is assayed by recovery of agglutination activity of the multivalent 5-factor after the univalent 21-factor has been inactivated by treatment of the complex with alkali. The 5-factor 21-factor complex, purified on Sepharose 6B, is large (several million daltons) and heterogeneous. The three peaks of 5-factor activity contain a number of combining sites proportional to molecular size.In this paper, evidence is presented for complex formation in vitro between yeast glycoprotein mating factors. These cellwall factors determine the specificity of cellular recognition as the first step in mating. Thus, these factors may be considered "complementary" in the sense proposed by Emil Fisher (1) in his-analogy:... "dass Enzym und Glucosid wie Schloss und Schlussel" .... Shortly later, in 1913, Lillie (2) described an activity extracted from sea-urchin eggs that specifically agglutinated sperm cells and was therefore complementary to a sperm-surface component. These early ideas concerning preformed combining sites on macromolecules formed the basis of models proposed by Tyler (3) and Weiss (4) in which the specificity of cellular adhesion in tissue development was explained by the presence of complementary molecules on opposing cell surfaces which combined in a manner analogous to antigen-antibody complex formation. Subsequent studies of cell contact have been reviewed extensively (see refs. 5-16 and other papers in these volumes). In systems involving adhesion of identical cells, additional theoretical considerations and biophysical parameters have been proposed (17-21). Current research in cellular recognition is centered on the identification and characterization of cell-surface aggregation factors isolated from diverse systems (22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). In general, the information for the specificity of aggregation factors is considered to reside in the primary sequence of the protein moiety. However, the role played by the carbohydrate moieties may be nontrivial since most of the aggregation factors studied thus far either interact with carbohydrates or glycoproteins on the cell surface or are glycoproteins themselves. The latter is true for the mating factors isolated from sexually agglutinative mating types of the yeast Hansenula wingei (34). This mating system has been reviewed (34), and criteria for determining specificity in other cell-aggregating systems were proposed (35). The hypothesis that the haploid mating factors are mutually repressed in the nonagglutinative diploid (36) has been supported by recent work in which conditions for the differential induction of each glycoprotein mating factor in the diploid were discovered (37).The mating factor from strain 5, called 5-factor (5f) (38) or ...

Sexual behavior and its pheromonal regulation in ascosporogenous yeasts

“…1975, HAGIYA et al 1977, purified, and found to be glycoproteins , HAGIYA 1980. Furthermore, molecular complexes of the released agglutination substances have been demonstrated in both yeasts (CRANDALL et al 1974. This is strong evidence to support the ligand hypothesis of sexual agglutination.…”

Morphological change in the early stages of the mating process of Rhodosporidium toruloides

“…FIG. 6. Mating tube formation in M-919 cells by supplement of a factor, the culture fluid of the mating tube-formed M-1057.…”

Sexual agglutination in budding yeasts: structure, function, and regulation of adhesion glycoproteins.

“…Intermolecular complexes of agglutinins from opposite mating types have been observed in H. wingei, S. kluyveri, and S. cerevisiae (14,16,28,67), indicating that the agglutinins interact directly with each other, i.e., that the agglutinins are involved in complementary interactions. The nature and properties of the interactive bonds in complexes of purified agglutinins are similar to those of cell-cell bonds formed between intact cells (9, 89, 116).…”