Structure of the bacterial flagellar protofilament and implications for a switch for supercoiling.
The bacterial flagellar filament is a helical propeller constructed from 11 protofilaments of a single protein, flagellin. The filament switches between left- and right-handed supercoiled forms when bacteria switch their swimming mode between running and tumbling. Supercoiling is produced by two different packing interactions of flagellin called L and R. In switching from L to R, the intersubunit distance ( approximately 52 A) along the protofilament decreases by 0.8 A. Changes in the number of L and R protofilaments govern supercoiling of the filament. Here we report the 2.0 A resolution crystal structure of a Salmonella flagellin fragment of relative molecular mass 41,300. The crystal contains pairs of antiparallel straight protofilaments with the R-type repeat. By simulated extension of the protofilament model, we have identified possible switch regions responsible for the bi-stable mechanical switch that generates the 0.8 A difference in repeat distance.
Protonic NanoMachine Project, ERATO, JST, 3-4 Hikaridai, Seika, Kyoto 619-0237, Japan.
F A
FA
Samatey
K
K
Imada
S
S
Nagashima
F
F
Vonderviszt
T
T
Kumasaka
M
M
Yamamoto
K
K
Namba
D018360:Crystallography, X-Ray; D005408:Flagellin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D020409:Molecular Motor Proteins; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D021381:Protein Transport; D012486:Salmonella typhimurium / Q000737:chemistry
D020409:Molecular Motor Proteins; D010446:Peptide Fragments; D005408:Flagellin