Prokaryotic expression and molecular characterization of surface antigen 3 (SAG 3) protein of Toxoplasma gondii

Abstract

Toxoplasmosis, caused by Toxoplasma gondii , is an important zoonotic disease with worldwide prevalence. In the present communication, we report molecular cloning, heterologous expression and characterization of 1158 bp complete open reading frame (ORF) of surface antigen 3 (SAG3) of T. gondii, RH strain, IVRI stock for the first time from India. The rSAG3 protein was expressed in E. coli as a 46kDa histidine-tagged fusion protein. Sequence analysis of the SAG3 coding sequence revealed 99.9% homology with the published sequence of T. gondii RH strain with substitution of a single base adenosine 'A' with guanosine 'G' at nucleotide position 397 in the ORF. Substitution of a single nucleotide resulted in substitution of aspartic acid (D) residue replacing asparagine (N).