Structure and Functional Study on HigBA from Streptococcus pneumoniae

Abstract

Streptococcus pneumoniae is a gram-positive strain that causes diseases mainly through respiratory infections. Diseases caused by pneumococcal species are meningitis, bacteremia, pneumonia, otitis and sinusitis. Patients infected with s.pneumonia have developed antibiotic resistant strains, so new antibiotics need to be developed. Ultimately, developing novel antibiotic candidates through structural analysis and functional studies of proteins is a major goal. The target TA complex protein present in the s.pneumoniae TIGR4 strain is a type II toxin-antitoxin system and is classified under HigBA family. The toxin protein HigB is predicted to be a ribosome-dependent mRNA interferases, which cleave mRNAs at the ribosomal A site. The antitoxin protein HigA regulates transcription through binding of palindromic sequence to its operator region. In order to obtain the tertiary structure of the protein, the target protein was obtained by recombinant process and was over-expressed in Rosetta (DE3) pLysS of escherichia coli. Affinity chromatography was used to purify the hexa-histidine tagged protein. Further, higher purity of target protein was obtained by ion-exchange chromatography and size-exclusion chromatography. The structure of target protein was obtained using X-ray crystallography techniques.