MOLECULAR CHARACTERIZATION OF THE SEC1 GENE OF SACCHAROMYCES-CEREVISIAE - SUBCELLULAR-DISTRIBUTION OF A PROTEIN REQUIRED FOR YEAST PROTEIN SECRETION

Strains of Saccharomyces cerevisiae harbouring temperature-sensitive m utations in the SEC1 and SEC5 genes exhibit an accumulation of post-Go lgi secretory vesicles at 37-degrees-C. We have cloned a fragment of y east DNA which carries two distinct genes, one of which complements a sec1 mutation, and the other a sec5 mutation. Genetic tests confirm th at the sec1-complementing gene is indeed SEC1, and is essential for ce ll growth. Nucleotide sequence analysis reveals that the cloned SEC1 g ene is the same as a previously sequenced sec1-complementing gene. The SEC1 sequence encodes a protein of 724 amino acids with a predicted m olecular mass of 83 kDa. Antibodies purified from a polyclonal antiser um raised against the protein product of the cloned gene recognize a y east protein of apparent molecular mass 78 kDa which is found in a det ergent-resistant association with a rapidly sedimenting yeast subcellu lar fraction, behaviour which is suggestive of an interaction with a c omponent of the yeast cytoskeleton.