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Functional dissection of N-acetylglutamate synthase (ArgA) of Pseudomonas aeruginosa and restoration of its ancestral N-acetylglutamate kinase activity

AuthorsSancho-Vaello, Enea ; Fernández-Murga, María L.; Rubio, Vicente
Issue Date23-Mar-2012
PublisherAmerican Society for Microbiology
CitationJournal of Bacteriology 194(11): 2791-801 (2012)
AbstractIn many microorganisms, the first step of arginine biosynthesis is catalyzed by the classical N-acetylglutamate synthase (NAGS), an enzyme composed of N-terminal amino acid kinase (AAK) and C-terminal histone acetyltransferase (GNAT) domains that bind the feedback inhibitor arginine and the substrates, respectively. In NAGS, three AAK domain dimers are interlinked by their N-terminal helices, conforming a hexameric ring, whereas each GNAT domain sits on the AAK domain of an adjacent dimer. The arginine inhibition of Pseudomonas aeruginosa NAGS was strongly hampered, abolished, or even reverted to modest activation by changes in the length/sequence of the short linker connecting both domains, supporting a crucial role of this linker in arginine regulation. Linker cleavage or recombinant domain production allowed the isolation of each NAGS domain. The AAK domain was hexameric and inactive, whereas the GNAT domain was monomeric/dimeric and catalytically active although with ∼50-fold-increased and ∼3-fold-decreased K(m)(glutamate) and k(cat) values, respectively, with arginine not influencing its activity. The deletion of N-terminal residues 1 to 12 dissociated NAGS into active dimers, catalyzing the reaction with substrate kinetics and arginine insensitivity identical to those for the GNAT domain. Therefore, the interaction between the AAK and GNAT domains from different dimers modulates GNAT domain activity, whereas the hexameric architecture appears to be essential for arginine inhibition. We proved the closeness of the AAK domains of NAGS and N-acetylglutamate kinase (NAGK), the enzyme that catalyzes the next arginine biosynthesis step, shedding light on the origin of classical NAGS, by showing that a double mutation (M26K L240K) in the isolated NAGS AAK domain elicited NAGK activity
Description11 páginas, 7 figuras, 1 tabla.
Publisher version (URL)http://dx.doi.org/10.1128/JB.00125-12
Appears in Collections:(IBV) Artículos
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J Bacteriol 2012-194-2791 Supp Inf.pdfInformación suplementaria247,37 kBAdobe PDFThumbnail
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