Summer Research Fellowship Programme of India's Science Academies

Purification and characterization of CcdB Protein in wild type and mutant type of Escherichia coli

Aishwarya Khamari

Gangadhar Meher University, Sambalpur 768004

Prof. Raghavan Varadarajan

Molecular Biophysics Unit, Indian Institute of Sciences, Bangalore 560012


The toxin-antitoxin (TA) system that is the best studied in Escherichia coli is the F-plasmid-based CcdAB system. It is involved in plasmid maintenance through postsegregational killing. CcdAB homologs have been found on the chromosome of a wild type and mutant type of E.coli. We show that purification, quantification and thermal stability characterization, both in case of wild type and mutant type (CcdB D67T) of CSH501 strain of E.coli. CcdB (Controller if Cell Division or Death B protein) toxin is a potent DNA Gyrase inhibitor, and leads to bacterial cell death even under a fullyrepressed condition. Our studies clearly demonstrate that the CcdA antitoxin specifically binds only to the CcdB toxin protein. The specific binding of CcdA to the CcdB results in prevention the binding of CcdB with the DNA-Gyrase.

The L-arabinose operon, also called the ara, is an opernon required for the breakdown of the five-carbon sugar, L-arabinose, in Escherichia coli . The L-arabinose operon contains three structural genes: araB, araA, araD (collectively known as araBAD), which encode for three metabolic enzymes ‚Äčthat are required for the metabolism of L-arabinose. The AraB (ribonuclease), AraA (an isomerasea), AraD (an epimerase) produced by these genes, catalyse conversion of L-arabinose to an intermediate of the pentose phosphate pathway, D-xylulose-5-phosphate.

Keywords: TA System, CcdAB, CcdA, CcdB, F-plasmid, CSH501, DNA-Gyrase, L-arabinose

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