tailieunhanh - Báo cáo khoa học: The N-acetylglutamate synthase/N-acetylglutamate kinase metabolon of Saccharomyces cerevisiae allows co-ordinated feedback regulation of the first two steps in arginine biosynthesis

In Saccharomyces cerevisiae, which uses the nonlinear pathway of arginine biosynthesis, the first two enzymes, N-acetylglutamate synthase (NAGS) andN-acetylglutamate kinase (NAGK), are controlled by feedback inhibition. We have previously shown that NAGS andNAGKassociate in a complex, essential to synthase activity and protein level [Abadjieva,A., Pauwels,K.,Hilven, P.&Crabeel,M. (2001) , 42869–42880]. | Eur. J. Biochem. 270 1014-1024 2003 FEBS 2003 doi The W-acetylglutamate synthase W-acetylglutamate kinase metabolon of Saccharomyces cerevisiae allows co-ordinated feedback regulation of the first two steps in arginine biosynthesis Katia Pauwels Agnes Abadjieva Pierre Hilven Anna Stankiewicz and Marjolaine Crabeel Department of Genetics and Microbiology of the Vrije Universiteit Brussel Brussels Belgium In Saccharomyces cerevisiae which uses the nonlinear pathway of arginine biosynthesis the first two enzymes N-acetylglutamate synthase NAGS and N-acetylglutamate kinase NAGK are controlled by feedback inhibition. We have previously shown that NAGS and NAGK associate in a complex essential to synthase activity and protein level Abadjieva A. Pauwels K. Hilven P. Crabeel M. 2001 J. Biol. Chem. 276 42869-42880 . The NAGKs of ascomycetes possess in addition to the catalytic domain that is shared by all other NAGKs and whose structure has been determined a C-terminal domain of unknown function and structure. Exploring the role of these two domains in the synthase kinase interaction we demonstrate that the ascomycete-specific domain is required to maintain synthase activity and protein level. Previous results had suggested a participation of the third enzyme of the pathway N-acetylglutamylphosphate reductase in the metabolon. Here genetic analyses conducted in yeast at physiological level or in a heterologous background clearly demonstrate that the reductase is dispensable for synthase activity and protein level. Most importantly we show that the arginine feedback regulation of the NAGS and NAGK enzymes is mutually interdependent. First the kinase becomes less sensitive to arginine feedbackinhibition in the absence of the synthase. Second and as in Neurospora crassa in a yeast kinase mutant resistant to arginine feedbackinhibition the synthase becomes feedbackresistant concomitantly. We conclude that the NAGS NAGK metabolon promotes the .