Photos from the 2003 East Tennessee Collegiate Division Meeting of the Tennessee Academy of Science held at Pellissippi State Technical Community College
4/11/2003
Anthony Jones and Brad Rogers, Carson Newman
Third Place Outstanding Undergraduate Presentation
ABSTRACT
Alteration of Ste2p activity in yeast mutants deficient in sphingomyelin and ergosterol
There are two functional mating types of the yeast Saccharomyces cerevisiae, MATa and MAT . The MATa cells release the -pheromone in pre-copulatory situations, whereas the MAT cell type releases the a-pheromone. The membrane protein in MATa cells which are responsible for the binding of the -pheromone is the G-protein coupled receptor (GPCR) known as Ste2p. Binding of the -pheromone by Ste2p induces arrest of cell growth and initiates a signal transduction cascade in preparation for conjugation of the two cell types. Not much is known about the regulation of the Ste2p receptor, but past evidence has shown that membrane lipids may be involved in its functionality. Various yeast strains were genetically transformed by homologous recombination to remove the genetic sequence for key enzymes in the biosynthetic pathways of sphingomyelin and ergosterol. These genes were SUR2 and ERG6, respectively. The mutants typically grew slower than the wild-type strains in complete media. Interestingly, the SUR2 mutants, which were deficient in sphingolipids, were less sensitive to drugs that inhibit ergosterol synthesis. Growth inhibition assays involving -pheromone indicated an altered sensitivity of the receptor. Data suggests that sphingomyelin and/or ergosterol may play a role in the activity of Ste2p. We are also looking at other measurements of receptor activity in an attempt to determine the underlying mechanisms of these effects.
