Dual regulation of the synthesis of the arginine pathway carbamoylphosphate synthase of Saccharomyces cerevisiae by specific and general controls of amino acid biosynthesis. |
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Authors: | André Piérard Francine Messenguy André Feller and François Hilger |
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Institution: | (1) Laboratoire de Microbiologie, Faculté des Sciences, Université Libre de Bruxelles, 1, Avenue E. Gryzon, B-1070 Bruxelles, Belgium;(2) Institut de Recherches, C.E.R.I.A., 1, Avenue E. Gryzon, B-1070 Bruxelles, Belgium;(3) Chaire de Microbiologie, Faculté des Sciences Agronomiques de l'Etat, B-5800 Gembloux, Belgium |
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Abstract: | Summary The synthesis of the arginine pathway carbamoylphosphate synthase (CPSase A) of Saccharomyces cerevisiae is subject to two control mechanisms. One mechanism is specific for CPSase A and is exerted by arginine; it probably involves a repressoroperator type of interaction. This specific mechanism regulates the expression of gene cpaI coding for the small glutaminase subunit of CPSase A but has little influence on the production of the large subunit of the enzyme, a product of gene cpaII. This large component, which alone has no biological significance, accumulates freely under conditions of arginine repression. The second mechanism is general: it controls enzyme synthesis in a number of amino acid biosynthetic pathways in addition to the arginine sequence. Two types of evidence that this general mechanism participates in the control of CPSase A synthesis are presented: (1) Derepression upon starvation for any amino acid of which the synthesis is subject to this general control; and (2) repression during growth in amino acid-rich medium. In contrast to the specific mechanism, the general mechanism regulates the expression of both the cpaI and cpaII genes. |
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