X-ray structure of TMP kinase from Mycobacterium tuberculosis complexed with TMP at 1.95 angstrom resolution

The X-ray structure of Mycobacterium tuberculosis TMP kinase at 1.95 Angstr om resolution is described as a binary complex with its natural substrate T NM. Its main features involve: (i) a clear magesium-binding site; (ii) an a lpha-helical conformation for the so-called LID region; and (iii) a high de nsity of positive charges in the active site. There is a network of interac tions involving highly conserved side-chains of the protein, the magnesium ion, a sulphate ion mimicking the beta phosphate group of ATF and the TMP m olecule itself. All these interactions conspire in stabilizing what appears to be the closed form of the enzyme. A complete multialignement of all (32 ) known sequences of TMP kinases is presented. Subtle differences in the TM P binding site were noted, as compared to the Escherichia coli, yeast and h uman enzyme structures, which have been reported recently. These difference s could be used to design specific inhibitors of this essential enzyme of n ucleotide metabolism. Two cases of compensatory mutations were detected in the TMP binding site of eukarotic and prokaryotic enzymes. In addition, an intriguing high value of the electric field is reported in the vicinity of the phosphate group of TMP and the putative binding site of the gamma phosp hate group of ATP. (C) 2001 Academic Press.