Metabolic and Regulatory Changes Associated with Growth of Saccharomyces cerevisiae in 1.4 M NaCl

Abstract

The salt-instigated protein expression of Saccharomy- ces cerevisiae during growth in either 0.7 or 1.4 M NaCl was studied by two-dimensional polyacrylamide gel electrophoresis. The 73 protein spots that were identi- fied as more than 3-fold responsive in 1.4 M NaCl were further grouped by response class (halometric, low-salt, and high-salt regulation). Roughly 40% of these respon- sive proteins were found to decrease in expression, while at higher magnitudes of change (>8-fold) only in- duction was recorded. Enolase 1 (Eno1p) was the most increasing protein by absolute numbers per cell, but not by -fold change, and the enzymes involved in glycerol synthesis, Gpd1p and Gpp2p, were also induced to a similar degree as Eno1p. We furthermore present evi- dence for salt induction of glycerol dissimilation via dihydroxyacetone and also identify genes putatively en- coding the two enzymes involved; dihydroxyacetone ki- nase (DAK1 and DAK2) and glycerol dehydrogenase (YPR1 and GCY1). The GPD1, GPP2, GCY1, DAK1, and ENO1 genes all displayed a halometric increase in the amount of transcript. This increase was closely linked to the salt-induced rate of protein synthesis of the corre- sponding proteins, indicating mainly transcriptional regulation of expression for these genes. A consensus element with homology to the URS sequence of the ENO1 promoter was found in the promoters of the GPD1, GPP2, GCY1, and DAK1 genes.