Insight on an Arginine Synthesis Metabolon from the Tetrameric Structure of Yeast Acetylglutamate Kinase

N-acetyl-L-glutamate kinase (NAGK) catalyzes the second, generally controlling, step of arginine biosynthesis. In yeasts, NAGK exists either alone or forming a metabolon with N-acetyl-L-glutamate synthase (NAGS), which catalyzes the first step and exists only within the metabolon. Yeast NAGK (yNAGK) has, in addition to the amino acid kinase (AAK) domain found in other NAGKs, a ∼150-residue C-terminal domain of unclear significance belonging to the DUF619 domain family. We deleted this domain, proving that it stabilizes yNAGK, slows catalysis and modulates feed-back inhibition by arginine. We determined the crystal structures of both the DUF619 domain-lacking yNAGK, ligand-free as well as complexed with acetylglutamate or acetylglutamate and arginine, and of complete mature yNAGK. While all other known arginine-inhibitable NAGKs are doughnut-like hexameric trimers of dimers of AAK domains, yNAGK has as central structure a flat tetramer formed by two dimers of AAK domains. These dimers differ from canonical AAK dimers in the −110° rotation of one subunit with respect to the other. In the hexameric enzymes, an N-terminal extension, found in all arginine-inhibitable NAGKs, forms a protruding helix that interlaces the dimers. In yNAGK, however, it conforms a two-helix platform that mediates interdimeric interactions. Arginine appears to freeze an open inactive AAK domain conformation. In the complete yNAGK structure, two pairs of DUF619 domains flank the AAK domain tetramer, providing a mechanism for the DUF619 domain modulatory functions. The DUF619 domain exhibits the histone acetyltransferase fold, resembling the catalytic domain of bacterial NAGS. However, the putative acetyl CoA site is blocked, explaining the lack of NAGS activity of yNAGK. We conclude that the tetrameric architecture is an adaptation to metabolon formation and propose an organization for this metabolon, suggesting that yNAGK may be a good model also for yeast and human NAGSs

Etude in vivo du rétrocontrôle de perméases d'acides aminés chez la levure

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Etude in vivo du rétrocontrôle de perméases d'acides aminés chez la levure

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe

Synthesis in vitro of Escherichia coli carbamoylphosphate synthetase

SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe

Participation in Saccharomyces cerevisiae of a post-transcriptional control in the synthesis of carbamoylphosphate synthase of the arginine pathway

SCOPUS: NotDefined.jinfo:eu-repo/semantics/publishe

Transport of arginine and ornithine into isolated mitochondria of Saccharomyces cerevisiae.

peer reviewedIn this work we have characterised the transport of L-arginine and L-ornithine into mitochondria isolated from a wild-type Saccharomyces cerevisiae strain and an isogenic arg11 knock-out mutant. The Arg11 protein (Arg11p) is a mitochondrial carrier required for arginine biosynthesis [Crabeel, M., Soetens, O., De Rijcke, M., Pratiwi, R. & Pankiewicz, R. (1996) J. Biol. Chem. 271, 25011-25019]. Reconstitution experiments have confirmed that it is an L-ornithine carrier also transporting L-arginine and L-lysine by order of decreasing affinity, but not L-histidine [Palmieri, L., De Marco, V., Iacobazzi, V., Palmieri, F., Runswick, M. & Walker, J. (1997) FEBS Lett. 410, 447-451]. Evidence is presented here that the mitochondrial inner membrane contains an L-arginine and L-ornithine transporting system distinct from Arg11p, in keeping with the arginine leaky phenotype of arg11 knock-out mutants. The newly characterised carrier, which we propose to name Bac1p (basic amino acid carrier), behaves as an antiporter catalysing the electroneutral exchange of the basic amino acids L-arginine, L-lysine, L-ornithine and L-histidine and displays the highest affinity for L-arginine (Km of 30 microM). L-Arginine uptake has a pH optimum in the range of 7.5-9 and is inhibited by several sulphydryl reagents, by pyridoxal 5'-phosphate and by cation

Control-mechanisms acting at the transcriptional and post-transcriptional levels are involved in the synthesis of the arginine pathway carbamoylphosphate synthase of yeast.

In Saccharomyces cerevisiae, the synthesis of the arginine pathway enzyme carbamoylphosphate synthase (CPSase A) is subject to two control mechanisms. One mechanism, the general control of amino acid biosynthesis, influences the expression of both CPA1 and CPA2 genes, the structural genes for the two subunits of the enzyme. The second mechanism, the specific control of arginine biosynthesis, only affects the expression of CPA1. To study these mechanisms in more detail, we have cloned the CPA1 and CPA2 genes and used their DNA to measure the CPA1 and CPA2 mRNA content of cells grown under various conditions. A close coordination was observed in the variation of the levels of CPA1 and CPA2 mRNAs and polypeptide products under conditions where the general control of amino acid biosynthesis operates. In contrast, little correlation was found between the levels of CPA1 mRNA and the corresponding protein for conditions affecting repression by arginine: the total amplitude of variation was 6-fold higher for the CPA1 protein than for the CPA1 messenger transcript. Such findings are consistent with the conclusion that the general control operates at the transcriptional level and that the specific arginine control acts primarily at a post-transcriptional level.SCOPUS: ar.jinfo:eu-repo/semantics/publishe