000096017 001__ 96017 000096017 005__ 20201029122510.0 000096017 0247_ $$2doi$$a10.1074/jbc.M113.462440 000096017 0248_ $$2sideral$$a114329 000096017 037__ $$aART-2013-114329 000096017 041__ $$aeng 000096017 100__ $$0(orcid)0000-0002-4254-3148$$aGarcía-Nafría, Javier 000096017 245__ $$aCrystal and Solution Studies Reveal That the Transcriptional Regulator AcnR ofCorynebacterium glutamicumIs Regulated by Citrate-Mg2+Binding to a Non-canonical Pocket 000096017 260__ $$c2013 000096017 5060_ $$aAccess copy available to the general public$$fUnrestricted 000096017 5203_ $$aCorynebacterium glutamicum is an important industrial bacterium as well as a model organism for the order Corynebacteriales, whose citric acid cycle occupies a central position in energy and precursor supply. Expression of aconitase, which isomerizes citrate into isocitrate, is controlled by several transcriptional regulators, including the dimeric aconitase repressor AcnR, assigned by sequence identity to the TetR family. We report the structures of AcnR in two crystal forms together with ligand binding experiments and in vivo studies. First, there is a citrate-Mg<sup>2+</sup> moiety bound in both forms, not in the canonical TetR ligand binding site but rather in a second pocket more distant from the DNA binding domain. Second, the citrate-Mg<sup>2+</sup> binds with a K<inf>D</inf> of 6 mM, within the range of physiological significance. Third, citrate-Mg<sup>2+</sup> lowers the affinity of AcnR for its target DNA in vitro. Fourth, analyses of several AcnR point mutations provide evidence for the possible involvement of the corresponding residues in ligand binding, DNA binding, and signal transfer. AcnR derivatives defective in citrate-Mg <sup>2+</sup> binding severely inhibit growth of C. glutamicum on citrate. Finally, the structures do have a pocket corresponding to the canonical tetracycline site, and although we have not identified a ligand that binds there, comparison of the two crystal forms suggests differences in the region of the canonical pocket that may indicate a biological significance. ¬© 2013 by The American Society for Biochemistry and Molecular Biology, Inc. 000096017 540__ $$9info:eu-repo/semantics/openAccess$$aby$$uhttp://creativecommons.org/licenses/by/3.0/es/ 000096017 590__ $$a4.6$$b2013 000096017 591__ $$aBIOCHEMISTRY & MOLECULAR BIOLOGY$$b65 / 291 = 0.223$$c2013$$dQ1$$eT1 000096017 655_4 $$ainfo:eu-repo/semantics/article$$vinfo:eu-repo/semantics/publishedVersion 000096017 700__ $$aBaumgart, Meike 000096017 700__ $$aTurkenburg, Johan P. 000096017 700__ $$aWilkinson, Anthony J. 000096017 700__ $$aBott, Michael 000096017 700__ $$aWilson, Keith S. 000096017 773__ $$g288, 22 (2013), 15800 -15812$$pJ. biol. chem.$$tJournal of Biological Chemistry$$x0021-9258 000096017 8564_ $$s599213$$uhttps://zaguan.unizar.es/record/96017/files/texto_completo.pdf$$yVersión publicada 000096017 8564_ $$s37201$$uhttps://zaguan.unizar.es/record/96017/files/texto_completo.jpg?subformat=icon$$xicon$$yVersión publicada 000096017 909CO $$ooai:zaguan.unizar.es:96017$$particulos$$pdriver 000096017 951__ $$a2020-10-29-10:14:32 000096017 980__ $$aARTICLE