Conformational change of flagellin for polymorphic supercoiling of the flagellar filament

• Published in: Nature structural & molecular biology Vol. 17; no. 4; pp. 417 - 422
• Main Authors: Maki-Yonekura, Saori, Yonekura, Koji, Namba, Keiichi
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.04.2010; Nature Publishing Group
• Subjects: 631/326/41/2536; 631/535/1258; 631/57/2272/2273; Bacteria; Bacterial Physiological Phenomena; Biochemistry; Biological Microscopy; Biomedical and Life Sciences; Cytoplasmic filaments; Flagella (Microbiology); Flagella - chemistry; Flagellin - chemistry; Genetic aspects; Life Sciences; Membrane Biology; Membranes; Motility; Physiological aspects; Polymorphism; Protein Conformation; Protein Structure; Japan
• ISSN: 1545-9993; 1545-9985
• DOI: 10.1038/nsmb.1774

Bacterial flagellar protofilaments can adopt 2 distinct conformations (L- or R-type), resulting in different functional states (the bacteria swim or tumble). The R-type protofilament was characterized previously by cryo-EM; now the same analysis of the L-type conformation provides insight into the conformational changes involved in this switch. The bacterial flagellar filament is a helical propeller rotated by the flagellar motor for bacterial locomotion. The filament is a supercoiled assembly of a single protein, flagellin, and is formed by 11 protofilaments. For bacterial taxis, the reversal of motor rotation switches the supercoil between left- and right-handed, both of which arise from combinations of two distinct conformations and packing interactions of the L-type and R-type protofilaments. Here we report an atomic model of the L-type straight filament by electron cryomicroscopy and helical image analysis. Comparison with the R-type structure shows interesting features: an orientation change of the outer core domains (D1) against the inner core domains (D0) showing almost invariant orientation and packing, a conformational switching within domain D1, and the conformational flexibility of domains D0 and D1 with their spoke-like connection for tight molecular packing.