Targeting of a heterologous protein to the cell wall of Saccharomyces cerevisiae

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Abstract
The sexual adhesion protein of Saccharomyces cerevisiae MATα cells, α‐agglutinin, could not be extracted from the cell wall with hot sodium dodecyl sulfate (SDS), but became soluble after digestion of the cell with laminarinase. This indicates that it is intimately associated with cell wall glucan. A fusion protein was constructed consisting of the signal sequence of yeast invertase, guar α‐galactosidase, and the C‐terminal half of the α‐agglutinin. Most of the fusion protein was incorporated in the cell wall. A small amount could be extracted with SDS, but most of it could only be extracted with laminarinase. On the other hand, cells containing a construct consisting of the signal sequence of invertase and α‐galactosidase released most of the α‐galactosidase into the medium and all cell wall‐associated α‐galactosidase was released by SDS. Labelling with antibodies showed that the α‐galactosidase part of the fusion protein was exposed on the surface of the cell wall. The results demonstrate that the C‐terminal half of the α‐agglutinin contains the information needed to incorporate a protein into the cell wall.