The bacterial flagellum is a complex nanomachine that provides motility through its action as an ion driven screw propeller. The flagellum is an essential virulence factor of many bacteria, including H. pylori, where motility is required to initiate and maintain a robust infection of the human epithelial gastric cells resulting in diseases such as gastric cancer, gastritis and duodenal ulcers.

Motor rotation is governed by the stator complex, which includes motility proteins A and B (MotB₂MotB₄) and forms a proton conduction channel. An active stator MotB component anchors to the peptidoglycan layer and the cytoplasmic memebrane simultaneously, via its C-terminal domain and the N-terminal transmembrane (TM) helix, respectively. Difficulties in the purification of membranous MotB lead to the engineering of a soluble chimeric N-terminally locked variant, with a view towards gaining structural information on the entire soluble structure of MotB. The native transmembrane helical region was replaced by a GCN4 leucine zipper motif from Saccharomyces cerevisia, with the expectation that it will mimic the TM domain, resulting in a soluble dimeric version of full length MotB.

Several techniques were used to characterise the chimeric variant including circular dichroism (CD), size exclusion chromatography, multi angle laser light scattering (SEC MALLS) and small angle X-ray scattering (SAXS). SAXS analysis allowed the placement of MotB domains previously solved by X-ray crystallography and the construction of a full length model. This initial structural characterisation of the full-length proteins MotB will help us further understand the activation mechanism of the stator complex.