Protein Domain : Flagellar hook-associated protein 1 IPR002371

Type	Family
Description	Within the bacterial flagellum, the basal-body rod, the hook, the hook- associated proteins (HAPs), and the helical filament together constitute an axial substructure whose elements share structural features and a common export pathway []. This entry represents the hook-associated protein 1 (HAP1, also known as FlgK) []. The structure of FlgK from Burkholderia pseudomallei has been revealed []. The amino acid sequences of the hook protein and of the three hook-associated proteins of Salmonella typhimurium have been deduced from the DNA sequences of their structural genes (flgE, flgK, flgL and fliD respectively). These sequences have been compared with each other and with those for the filament protein (flagellin) and four rod proteins. The hook protein was found to be most similar to the distal rod protein (FlgG) and theproximal hook-associated protein (HAP1), which are thought to be attached to the proximal and distal ends of the hook, the similarities being most pronounced near the N-and C-termini. It is thought that the axial proteins may adopt amphipathic α-helicalconformations at their N- and C-termini. These regions of the filament and hook are believed to be responsible for quaternary interactions betweensubunits. Interaction between N- and C-terminal α-helices may be important in the formation of the axial structures of the flagellum.Although consensus sequences have been noted, no consensus extends to the entire set of axial proteins. Thus the basis for recognition of a proteinfor export by the flagellum-specific pathway remains to be identified.
Short Name	FlgK