MOLECULAR-CLONING OF CWP1 - A GENE ENCODING A SACCHAROMYCES-CEREVISIAE CELL-WALL PROTEIN SOLUBILIZED WITH RAROBACTER-FAECITABIDUS PROTEASE-I

A yeast cell wall glycoprotein with a molecular weight of 40,000, name d gp40, was solubilized from SDS-extracted cell wall of Snccharomyces cerevisiae by incubation with Rarobacter faecitabidus protease I, whic h is a yeast-lytic enzyme, Based on its amino acid sequence, we cloned and sequenced the gene encoding the precursor of gp40, named CWP1; ce ll wall protein gene, The DNA sequence of the CWP1 gene was identical to YKL443, an open reading frame identified in a genome sequencing pro gram for yeast chromosome XI. This gene encoded a serine-rich protein of 239 amino acids with a molecular weight of 24,267. The presence of hydrophobic sequences in the N- and C-termini of the CWP1 protein sugg ests that it is secreted as a glycosylphosphatidylinositol-anchored pr otein and is subsequently integrated into the cell wall. Since a gene disruption experiment showed no growth defect, the CWP1 gene is not es sential for growth. Mutant CWP1 protein deficient in the C-terminal hy drophobic sequence was secreted into the culture medium, not anchored to the cell wall, thereby indicating that this hydrophobic sequence pl ays a crucial role in anchoring to the cell wall. Homology between the CWP1 protein and TIP1 family of cold shock proteins suggests that the y belong to a new family of cell wall proteins.