Abstract
The bacterial flagellar filament has been an important model system in structural biology. Current models are based upon the notion that subunits can switch between two stable states, one forming left-handed 11-start protofilaments and the other forming right-handed ones (Calladine, 1975; Kamiya et al., 1980). Pioneering work on the structure of two flagellin mutants came from the Namba lab, studying the Salmonella filament (Maki-Yonekura et al., 2010; Samatey et al., 2001). We have been using cryo-EM to study the structure of a gram-positive bacterium, Bacillus subtilis. We have now reconstructed five mutants, all at a better resolution than obtained for Salmonella. For one mutant, we have reached ∼ 3.6 A, which allows for a full atomic model to be built with a high-degree of confidence. These results are being combined into a new model for how structural polymorphism is dictated by the switching between two states, only possible with the recent advances allowing for near-atomic resolution reconstructions of these filaments.Calladine, C.R. (1975). Construction of bacterial flagella. Nature 255, 121-124.Kamiya, R., Asakura, S., and Yamaguchi, S. (1980). Formation of helical filaments by copolymerization of two types of ’straight‘ flagellins. Nature 286, 628-630.Maki-Yonekura, S., Yonekura, K., and Namba, K. (2010). Conformational change of flagellin for polymorphic supercoiling of the flagellar filament. NatStructMolBiol 17, 417-422.Samatey, F.A., Imada, K., Nagashima, S., Vonderviszt, F., Kumasaka, T., Yamamoto, M., and Namba, K. (2001). Structure of the bacterial flagellar protofilament and implications for a switch for supercoiling. Nature 410, 331-337.
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