A SER THR-RICH MULTICOPY SUPPRESSOR OF A CDC24 BUD EMERGENCE DEFECT

MSB2 was identified previously as a multicopy suppressor of a temperature-sensitive mutation in CDC24, a gene required for polarity establishment and bud formation in Saccharomyces cerevisiae. The inferred MSB2 product contains 1306 amino acids, 42% of which are Ser or Thr. Its Ser + Thr-richness and hydrophobicity profile suggest that Msb2p may be an integral membrane protein containing a long, periplasmic, N-terminal domain and a short, cytoplasmic, C-terminal domain. Cells that lack MSB2 display no obvious mutant phenotypes. MSB2 is located between the centromere and KSS1 on the right arm of chromosome VII. Although physical mapping suggests that MSB2 and LEU1 (on the left arm of chromosome VII) are approximately 40 kb apart, the genetic map distance observed between leu1 and an msb2:: URA3 marker was only 2.3 cM.