Transmembrane signalling in Saccharomyces cerevisiae.

Baker's yeast, a unicellular eukaryote, has been a model organism for biochemists, geneticists and most recently for molecular biologists. Pioneering biochemical studies were conducted on yeast, such as the study of glucose fermentation and amino acid metabolism. The powerful tools of yeast genetics have allowed a comprehensive study of important issues such as the cell cycle and meiosis. In recent years, it has been established that Saccharomyces cerevisiae, the most extensively characterized of the yeasts, shares key molecules and biochemical pathways with higher eukaryotes. For example, actin, tubulin, ubiquitin, calmodulin, GTP regulatory proteins, different protein kinases including protein tyrosine kinases, were all found to play central roles in yeast. Furthermore, structurally homologous proteins, as well as transcription regulating elements, of yeast and higher eukaryotes, including mammals, were shown to be structurally and functionally interchangeable. It has also been found that yeast can express human genes. Technically, yeasts are simple to handle, inexpensive to grow, complete a cell cycle within 90 min, and therefore can yield relatively quick results. These qualities are useful in biotechnological applications. Saccharomyces cerevisiae, can be genetically manipulated fairly easily, and has been tinkered with more than any other system. A cloned, in vitro mutated gene, can be transformed into wild type yeast and by homologous recombination, can replace the native gene and generate the desired mutant. Such manipulations, not possible yet in other eukaryotic cells, allow the precise definition of the role played by different genes and their domains. These unique features of Saccharomyces cerevisiae, together with rapidly evolving techniques of molecular biology, have made it a successful model organism for the study of numerous questions.(ABSTRACT TRUNCATED AT 250 WORDS)