The binding of trimethoprim to bacterial dihydrofolate reductase

The charge state of trimethoprim bound to Lactobacillus casei dihydrofolate reductase

“…[23]) this statement can be made with some confidence; it is clearly consistent with recent crystallographic work [ 15 ]. This close similarity in the binding of the corresponding parts of trimethoprim and methotrexate justifies one of the central assumptions of our analysis of the proton chemical shift changes of trimethoprim on binding [18], and indeed one of the two possible conformations for trimethoprim bound to the enzyme in solution proposed from this analysis [18] is very similar to that subsequently found crystallographically [15].…”

“…The recent determination of the crystal structure of the enzyme-trimethoprim complex [15] shows that the orientation of the 2,4-diaminopyrimidine ring in the binding site is very similar to that of the analogous part of methotrexate [11,16]. We now report ~3C NMR experiments which confirm this similarity in the binding of the two inhibitors in solution, and show that trimethoprim is also protonated when bound.…”

“…Two other probable contributions can be identified. In the crystal, the carboxylate of Asp-26 (L. casei numbering) is close to N1 of bound methotrexate [11,1 6] or trimethoprim [15]. This interaction is doubtless responsible for the increase in pK of these ligands on binding, but the proximity of the carboxylate group will also lead to an electric field shift of the 2-13C resonance, whose sign wilt depend on the relative polarisability of the bonds to this carbon [19][20][21].…”

The structure of mouse L1210 dihydrofolate reductase‐drug complexes and the construction of a model of human enzyme

“…The three-dimensional structures of DHFRs from several sources have been extensively studied [4][5][6][7][8][9][10][11]. In order to understand better the structural basis of drug selectivity and to apply this knowledge to the design of novel inhibitors, an Xray study of DHFR from mouse L1210 tumour cells was undertaken.…”

Structures of two active trimethoprim analogues: 2,4-diamino-5-(4-isopropenyl-3,5-dimethoxybenzyl)pyrimidinium ethanesulfonate, C16H21N4O2+.C2H5O3S− (I), and 2,4-diamino-5-(3,5-dimethoxy-4-methoxycarbonylbenzyl)pyrimidine, C15H18N4O4 (II)

“…The structure of trimethoprim bound to bacterial and avian dihydrofolate reductase has been observed in crystal-structure complexes (Baker, Beddell, Champness, Goodford, Norrington, Smith & Stammers, 1981;Matthews & Volz, 1982). These studies show that, in the bacterial reductase binding site, TMP has an antiskewed conformation similar to that observed in the 4'-isopropenyl-TMP structure, while that in chicken liver DHFR is twist, similar to the conformation of the 4'-methoxycarbonyl-TMP structure.…”