A H"+ - ATPase da membrana plasmatica e a resposta ao stress oxidativo, em particular ao stress pelo cobre, em Saccharomyces Cerevisiae

The H"+ - ATPase in the plasma membrane of Saccharomyces cerevisiae is activated in exponential cells grown under mild copper stress (3 times) and in copper-induced latency cells (10 times) and the mechanisms involved in this activation were analysed. For copper concentrations close to the maximal that allowed growth, the activity of this proton pump declined, however, as the result of plasma membrane disorganisation by Cu"2"+ - induced oxidative stress and was correlated with copper tolerance. Maximal specific activities were found for intermediary copper concentrations, that lead to the increase of antioxidant enzymes activities, and to the decrease of oxidative damages. Despite the fact that the transcriptional activators, Msn2 and Msn4, were required for the adaptation to the copper-induced lag phase and growth resumption, they were not required for the strong plasma membrane H"+ -ATPase activation accompanying the intracellular acidification during copper-induced latency. We also show that the increase of plasma membrane H"+ - ATPase activity during respiratory growth compared with fermentative growth, was due to the regulation at the transcriptional level. Taken together, all these results clearly indicate that the in vivo activation of plasma membrane H"+ - ATPase activity, induced by oxidative stress, is part, or the result, of the global response of yeast to stressAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1249-074 Lisboa, Portugal / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga