PLP1 is one of two S. cerevisiae genes encoding proteins similar to mammalian phosducins (1). Phosducins inhibit the GTPase activity of several heterotrimeric G proteins, presumably as a consequence of binding to the beta-gamma subunits of the G proteins (5, 6). In yeast, a heterotrimeric G protein comprising Gpa1p, Ste4p, and Ste18p transduces the mating pheromone signal (reviewed in reference 7). Both Plp1p and the second yeast phosducin, Plp2p, bind to the yeast G beta-gamma complex (Ste4p and Ste18p), suggesting that they may play a role in mating pheromone signal transduction (1). Overexpression of PLP1 or PLP2 reduces pheromone-responsive transcriptional activation, but has no effect on pheromone induced growth arrest (1). Although Plp1p is dispensable, Plp2p is essential for viability, and its essential role may be in a process other than mating (1). PLP1 exhibits genetic interactions with genes involved in folding of beta-tubulin and in assembly of alpha-beta tubulin (Tub1p-Tub2p) heterodimers, which are the basic components of microtubules (2). This suggests that Plp1p may have a role in folding of beta-tubulin, and that its similarity to phosducins may not be relevant to its biological function (2).

Last updated: 2000-04-13