FIG. 3. Bacterial flagellar filaments and polymorphism: (A) Structure of straight flagellar filament from a mutant of Salmonella typhimurium [24]. Reprinted with permission from O’Brien EJ, Bennett PM, “Structure of straight flagella from a mutant Salmonella”, J. Mol. Biol., 70 (1), 145-152, Copyright 1972 Elsevier. The L-type straight flagellar filament (left) has two types of helical grooves, left-handed long-pitch and right-handed short-pitch grooves, whereas the R-type straight filament (right) has right-handed long-pitch and left-handed short-pitch grooves. Examples of short-pitch grooves are marked by thin blue lines and indicated by arrows. (B) Schematic of some polymorphic states of the flagellar filament, from left to right: L-type straight, normal (left-handed shape), curly (right-handed) and R-type straight. The top panel shows the shape of the filaments while the bottom panel displays the arrangements of flagellin subunits. Examples of short-pitch grooves are marked by thin blue lines and indicated by arrows [25]. Reprinted with permission from Namba K, Vonderviszt F, “Molecular architecture of bacterial flagellum”, Q. Rev. Biophys., 1997, 30 (1), 1-65, Copyright 1997 Cambridge University Press.
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