Sexual agglutination in yeast: VII. Significance of the 1.7S component from reduced 5-agglutinin

Abstract

The sex-specific agglutinin from mating type 5 of Hansenula wingei was purified by absorption on and elution from cells of type 21. When purified 5-agglutinin was reduced with thiols, its ability to agglutinate type 21 was destroyed and approximately six small fragments ( s 25 = 1.7S, M = 12,000) were released from the major reduced component. Approximately five disulfide bonds were present in the average 5-agglutinin particle, as estimated from 35S label. Allowing for variation among different preparations, it appears that each particle of 1.7S component is linked to the major reduced component by one disulfide bond. After fractionation, neither the 1.7S reduced component nor the major one were specifically absorbed by type 21 cells, but mixtures of both components were partially absorbed by type 21 cells after the disulfide bonds had been reformed by oxidation. It is concluded that the 1.7S component is not the complete combining site of 5-agglutinin, but that both reduced components carry parts of the combining site, which is stabilized by the disulfide bond joining them.