Sexual agglutination factors from the yeast pichia amethionina

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Abstract
Pichia amethionina is a heterothallic yeast isolated from necrotic cactus tissue. Haploid cells of opposite mating type, designated a and α, agglutinate strongly when mixed. The agglutination factors of the two cell types have been solubilized from the cell walls by β‐glucanase digestion and then partially purified by affinity adsorption to the opposite cell type and by gel filtration. From α‐cells was obtained a large, heat‐stable glycoprotein with the ability to agglutinate a‐cells. This α‐agglutinin was inactivated by mercaptoethanol, probably because the recognition sites are linked to the glycoprotein core by disulfide bonds. Digestion of a‐cells with β‐glucanase released a large heat‐labile glycoprotein that did not agglutinate α‐cells but did inhibit agglutination of a‐cells by α‐agglutinin. Subtilisin digestion of this a‐factor released a carbohydrate‐free protein of 27,000 daltons that retained the biological activity of the factor. These agglutination factors are sex‐ and species‐specific and are not found on the surface of heterozygous diploid cells.