Amplification and bioinformatics analysis of Toxoplasma gondii BSR4 gene

Objective: To clone and identify the surface antigen BSR4 of Toxoplasma gondii (T. gondii) PRU strain,to match the homology of BSR4 among T. gondii PRU and ME49 strains,and to analyze the feature by bioinformatics. Methods: DNA of strain PRU of T. gondii was extracted, and a pair of specific primers were designed from sequence of T. gondii ME49 bradyzoite surface antigen BSR4 and used to amplify the BSR4 of T. gondii PRU strain by PCR,then cloned into vector pET28a (+) and sequencing. Predict the physical and chemical nature, structure and function of BSR4. Results: The target gene was amplified by PCR. The sequencing result showed that the fragment was 1 194 bp which encoded 398 amino acid. The deduce amino acid sequcence of PRU strain BSR4 gene showed a 100% homology with that of ME49 strain. The predicted BSR4 protein molecular weight is 42 344.75 Dalton which can form two functional domains with a signal peptide location before 40 amino acids. The N-terminal of BSR4 was a signal peptide and the C-terminal was a hydrophobic region which suggested it was a GPI-anchored surface protein. There were 18 potential antigenic epitopes and 2 conserved domains in BSR4. Conclusions: The sequence of bradyzoite-specific antigen BSR4 from T. gondii PRU strain was successfully cloned.