Improved expression and purification of the Helicobacter pylori adhesin BabA through the incorporation of a hexa-lysine tag.

Abstract Helicobacter pylori is a pathogenic bacterium that has the remarkable ability to withstand the harsh conditions of the stomach for decades. This is achieved through unique evolutionary adaptations, which include binding Lewis b antigens found on the gastric epithelium using the outer membrane protein BabA. We show here the yield of a recombinant form of BabA, comprising its putative extracellular binding domain, can be significantly increased through the addition of a hexa-lysine tag to the C-terminus of the protein. BabA was expressed in the periplasmic space of Escherichia coli and purified using immobilised metal ion affinity and size exclusion chromatography – yielding approximately 1.8 mg of protein per litre of culture. The hexa-lysine tag does not inhibit the binding activity of BabA as the recombinant protein was found to possess affinity towards HSA–Lewis b glycoconjugates.