Accumulation of processing intermediates of the RAS2 protein in strain 112 of Saccharomyces cerevisiae.

Strain 112 (RAS1 RAS2) contains a naturally occurring mutation which significantly retards processing of the RAS2 gene product. This mutation, resulting in the accumulation of precursor forms of RAS2 protein, has been assigned by genetic analysis to a single chromosomal locus distinct from the RAS2 locus. In addition to the known precursor molecule of 41000 daltons (p41), 112 cells accumulate within the soluble fraction an intermediate form of RAS2 (p40-1), which migrates, in SDS-polyacrylamide gel, between p41 and the fully processed, membrane-bound 40,000 daltons (p40) product. We propose for RAS2 protein processing the following sequence of events: p41 greater than p40-1 greater than p40 where p40-1 represents a RAS2 intermediate required for the targeting of the protein to the plasma membrane.