In silico Design of Truncated Omp31 Protein of Brucella melitensis: Its Cloning and High Level Expression in Escherichia coli

Introduction: Omp31 is animmunodominant and protective antigen conserved in Brucella species and a good candidate for vaccine design. Material methods: The present study aimed at in silico design of the truncated Omp31 (TOmp31) using bioinformatic tools and to express the selected form in Escherichia coli (E. coli) Results and conclusion: Various bioinformatically calculated scores for the model showed that the structure conformation of the truncated Omp31 is in the range of the native protein with the C score, Z score, TM score and Ramachandran Z score of the truncated form model being 0.53, 0.72 and 0.98 respectively. Amplification of TOmp31 produced a single fragment of approximately 345 bp which was cloned in the pET28a expression vector. The integrity of the constructed vector (pET28 TOmp31) was confirmed by PCR and restriction digestion analysis and the rTOmp31 was successfully expressed in E. coli BL21. SDS PAGE analysis of the lysate from the induced E. coli carrying the TOmp31 construct and the purified protein showed the expected molecular mass of approximately 12 kDa. The yield of the purified protein was estimated at approximately 250 μg/ml. Anti His antibody reacted with the purified protein in Western blot confirming its expression in the prokaryotic system. Future studies exploring the immunogenicity and cross protection of the protein against Brucella spp. are underway.