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Appl. Environ. Microbiol., May 1995, 1904-1909, Vol 61, No. 5
CA Viegas, PB Sebastiao, AG Nunes and I Sa-Correia
During exponential growth at temperatures of 30 to 39 degrees C, the
specific activity of H(+)-ATPase in the plasma membrane of Saccharomyces
cerevisiae (assayed at the standard temperature 30 degrees C) increased
with increases in growth temperature. In addition, the optimal temperature
for in vitro activity of this ATPase was 42 degrees C. Therefore, the
maximum values of ATPase activity were expected to occur in cells that grew
within the supraoptimal range of temperatures. Activation induced by
supraoptimal temperatures was not the result of increased synthesis of this
membrane enzyme. When the growth temperature increased from 30 to 40
degrees C, expression of the essential PMA1 gene, monitored either by the
level of PMA1 mRNA or the beta-galactosidase activity of the lacZ-PMA1
fusion, was reduced. Consistently, quantitative immunoassays showed that
the ATPase content in the plasma membrane decreased. Like ATPase activity,
the efficiency of the PMA2 promoter increased with increases in growth
temperature in cells that had been grown at 30 to 39 degrees C, but its
level of expression was several hundred-fold lower than that of PMA1. These
results suggest that the major PMA1 ATPase is activated at supraoptimal
temperatures.
Copyright © 1995, American Society for Microbiology
Activation of plasma membrane H(+)-ATPase and expression of PMA1 and PMA2 genes in Saccharomyces cerevisiae cells grown at supraoptimal temperatures
Laboratorio de Engenharia Bioquimica, Instituto Superior Tecnico, Lisbon, Portugal.
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