Crystal structure of the flagellin protein FlaG from Helicobacter pylori

Flagella, comprising flagellin proteins, are essential virulence factors for Helicobacter pylori to colonize human stomach mucosa. The flagellin‐associated flaG operon of H. pylori consists of the flaG , fliD , and fliS genes under the control of a σ 28 ‐dependent promoter. The flaG gene is involved in chemotaxis and motility. We cloned, expressed, and purified the H. pylori flaG gene encoding the flagellin protein Hp FlaG. Sequence alignment revealed that Hp FlaG exhibits low sequence identity with other FlaG proteins. Overall, N‐terminal sequences of FlaG proteins are mostly divergent, and C‐terminal regions might be important for dimer interactions between protein subunits. Here, we report the crystal structure of the N‐terminal truncated protein (NT‐ Hp FlaG), as determined by multiwavelength anomalous dispersion at a resolution of 2.7 å. The overall structure of NT‐ Hp FlaG consists of two helices and three strands, folded into a palm‐like conformation. Two monomers strongly interact as a dimer by hydrophobic coiled‐coil interactions. Based on our structure, we suggest that the functional state of Hp FlaG is as a dimer.