T. cruzi glutathionylspermidine synthethase (GspS): homology 3D modelling and molecular docking

GARAY AS; RODRIGUES DE; GUERRERO SA

Rio de Janeiro, Brasil

Congreso; VII Iberoamerican Congress of Biophysics 2009; 2009

T. CRUZI GLUTATHIONYLSPERMIDINE SYNTHETASE (GSPS):HOMOLOGY 3D MODELLING AND MOLECULAR DOCKING STUDYGaray, Alberto. S.a; Rodrigues, Daniel E.a,b; Guerrero, SergiocaDepartamento de Física, Facultad de Bioquímica y Ciencias Biológicas, UniversidadNacional del Litoral, C.C.242, S3000ZAA, Santa Fe, Argentina.bINTEC, Universidad Nacional del Litoral y CONICETcLaboratorio de Bioquímica Microbiana, Cátedra de Parasitología, Facultad deBioquímica y Cs. Biológicas,Universidad Nacional del Litoral, Santa Fe, Argentinae-mail: sgaray@fbcb.unl.edu.arTrypanosomatids utilize trypanothione to regulate intracellular thiol redoxbalance and protect against oxidative stress. Trypanothione biosynthesisrequires ATP-dependent conjugation of glutathione (GSH) to the two terminalamino groups of spermidine by glutathionylspermidine synthetase (GspS) andtrypanothione synthetase (TryS), which are considered as drug targets. GspScatalyzes the step before the last of the biosynthesis-amide bond betweenspermidine 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 fulfillthe same function. We build a 3D model of Tc-GspS based on a multiple sequencealignment (MSA) of E. coli GspS and Leishmania major TryS.The MSA showed that a Glutamic acid residue that is highly conserved in all ATPgraspproteins and also in our templates was mutated to Alanine in the Tcenzyme.The role of this residue has been described as vital in the enzymecatalysis because it bridges two magnesium atoms. We performed a comparativestudy 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 dockingscore 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 resultspose the question about the role of this enzyme in T. cruzi.