SUMMARY PARAGRAPH for RSR1
Rsr1p (Bud1p) is a ras-like GTPase required for the first step in budding, bud site selection (4). RSR1 was first identified as a high copy suppressor of a temperature sensitive mutation in the guanine nucleotide exchange factor CDC24 (6). Mutations in RSR1 result in a random budding pattern rather than the usual axial pattern in haploids and bipolar pattern in a/alpha diploids (1, 6). Rsr1p is also required for morphological changes in response to mating pheromone, and for efficient cell fusion (2, 3). Rsr1p is a small GTP-binding protein and shows significant similarity to many proteins in the ras superfamily, especially to mammalian Rap GTPases (5, 6, 7). Bud2p appears to be the GTPase-activating protein that negatively regulates Rsr1p, and Bud5p the GDP/GTP exchange factor that positively regulates it (8, 9, 1). Rsr1p has been found to interact with Cdc24p when Rsr1p is in its GTP-bound state, and with Bem1p when it is in its GDP-bound state (10). Rsr1p is associated with the plasma membrane, and is thought to interact with Bud2p, Bud5p, Cdc24p, and Bem1p at the site of future bud growth (4, 11).
Last updated: 1999-09-01