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

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.