PURIFICATION, CHARACTERIZATION AND EXPRESSION, OF RECOMBINANT OUTER MEMBRANE PROTEIN A (OMP A) OF ACINETOBACTER BAUMANNII LI311

Abstract

Acinetobacter baumannii is a known hospital aquired  pathogenic bacterium that increasingly resists antibiotics treatment. In order to characterize and produce a soluble OmpA protein that can be used to develop Acinetobacter vaccine, polymerase chain reaction (PCR) was used to produce the ompA gene, of A.  baumannii strain  LI311, which was cloned into the histidin taged pET19b expression plasmid. Immobilized metal affinity chromatography (IMAC) was utilized  to purify the recombinant protein, and amino acid sequences for OmpA protein homologs were attained from the National Center for Biotechnology Information (NCBI) protein resource then analyzed using  the blast  tool and Jalview program. Protein topology prediction was done using NCBI tools and PRED-TMBB2. Analysis of  amino acid sequence of OmpA of  A.  baumannii strain  LI311 showed that it  has homologies to  other clinical Acinetobacter spices , including: A. pittii , A.nosocomialis , A.seifertii, A. calcoaceticus,  and A. ursingii with identity  percentages of  100%, 100%, 96%, 92%, and 91%. Protein topology prediction revealed two conserved domains belonging  to OmpA  family protein ,which are beta-barrel domain outer membrane protein (OMP_b-brl) and OmpA-C-like domain, and it is a 10-βeta -stranded transmembrane Outer Membrane Protein with a signal peptide  at residues 1–22A. A recombinant Histidine tagged- OmpA (39.31kDa )was successfully  expressed and purified in this study.  In conclusion, OmpA  protein  of A.baumannii strain LI31 is highly conserved across clinical species of Acinetobacter, and the soluble recombinant OmpA created in this study can be used to develop a putative vaccine that may prevent infections caused by the clinical species of  Acinetobacter.