RESUMO
MIG1, encoding a C2H2 zinc-finger repressor protein involved in carbon catabolite repression, was found to play a role in non-sexual flocculation of Saccharomyces cerevisiae. Disruption of MIG1 in a flocculent mutant strain of NCYC 227, resulted in a non-flocculent phenotype. Expression of MIG1 on a 2 mu pRS426 vector in a non-flocculent strain, YM 4134, caused flocculation; MIG1 on a high-copy-number LEU2-d plasmid caused intense flocculation in the same strain. Mutations in the SSN6 and TUP1 genes confer a flocculent phenotype in non-flocculent strains of S. cerevisiae, and it has been shown that Mig1 can tether the Ssn6p-Tup1p complex to the regulatory regions of glucose-repressible genes. Mutations in tup1 in a MIG1 background caused flocculation while double mutants of TUP1 and MIG1 did not flocculate. Based on these results, a model for the role of MIG1 in flocculation gene regulation is proposed.
Assuntos
Proteínas de Ligação a DNA/genética , Floculação , Regulação Fúngica da Expressão Gênica , Proteínas Repressoras/genética , Saccharomyces cerevisiae/genética , Northern Blotting , Clonagem Molecular , Proteínas de Ligação a DNA/antagonistas & inibidores , Proteínas de Ligação a DNA/biossíntese , Testes de Floculação , Mutagênese/efeitos da radiação , Mutagênese Insercional , Plasmídeos , RNA Mensageiro/isolamento & purificação , Proteínas Repressoras/antagonistas & inibidores , Proteínas Repressoras/biossíntese , Saccharomyces cerevisiae/crescimento & desenvolvimento , Proteínas de Saccharomyces cerevisiaeRESUMO
In rapidly fermenting yeast, the rotenone insensitive mitochondrial NADH dehydrogenase was not completely repressed by high glucose. This activity appeared to enhance the glycolytic rate due to which acetaldehyde accumulated intracellularly. To overcome the toxicity of acetaldehyde, the strain produced stress proteins. During late stationary phase of growth, the accumulated acetaldehyde was converted to ethanol resulting in faster ethanol production.
Assuntos
Acetaldeído/farmacologia , Etanol/metabolismo , Mitocôndrias/enzimologia , NADH Desidrogenase/metabolismo , Saccharomyces cerevisiae/metabolismo , Eletroforese em Gel de Poliacrilamida , Glucose/farmacologia , Rotenona/farmacologiaRESUMO
A cell-wall-surface protein purified from the cells of Saccharomyces cerevisiae NCYC 227 was found to be involved in the non-sexual flocculation of this yeast. This 13 kDa protein was found to bind specifically to mannose. The protein bound to mannans isolated from yeast as well as in situ to intact cells, but only in the presence of calcium ions. The protein, a mannoprotein, formed aggregates as revealed in SDS-PAGE. Urea and higher temperatures prevented protein aggregation, suggesting that the flocculation of S. cerevisiae is primarily due to hydrogen bonding between mannan and protein.
