T. cruzi glutathionylspermidine synthetase (GSPS): homology 3D modelling and molecular docking study

GARAY, ALBERTO. S.; RODRIGUES, DANIEL E.; GUERRERO, SERGIO

Buzios, Río de Janeiro, Brasil

Congreso; Biophysics 2009, VII Congreso Iberoamericano de Biofísica; 2009

Sociedad de Biofísica de Brasil y Argentina, IUPAB

Trypanosomatids utilize trypanothione to regulate intracellular thiol redox balance and protect against oxidative stress. Trypanothione biosynthesis requires ATP-dependent conjugation of glutathione (GSH) to the two terminal amino groups of spermidine by glutathionylspermidine synthetase (GspS) and trypanothione synthetase (TryS), which are considered as drug targets. GspS catalyzes the step before the last of the biosynthesis-amide bond between spermidine and the glycine carboxylate of GSH. The 3D structure of the T. cruzi (Tc-) GspS has not been yet determined by X-ray, and it is not clear its role keeping in mind that this organism has TryS to fulfill the same function. We build a 3D model of Tc-GspS based on a multiple sequence alignment (MSA) of E. coli GspS and Leishmania major TryS. The MSA showed that a Glutamic acid residue that is highly conserved in all ATPgrasp proteins and also in our templates was mutated to Alanine in the Tcenzyme. The role of this residue has been described as vital in the enzyme catalysis because it bridges two magnesium atoms. We performed a comparative study of the docking of the ATP molecule in the binding sites of the E. coli GspS, its mutated variant (A330E), in our Tc-GspS 3D model and its variant (E345A). These studies show that: 1) the Alanine mutated E. coli GspS has a lower docking score than the native enzyme. 2) mutation of Alanine for Glutamic acid in T. cruzi GspS has a larger docking score than the native enzyme. These results pose the question about the role of this enzyme in T. cruzi.