Structural and Functional Analysis of the C-Terminal Region of FliG, an Essential Motor Component of Vibrio Na+-Driven Flagella
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The flagellar motor protein complex consists of rotor and stator proteins. Their interaction generates torque of flagellum, which rotates bidirectionally, clockwise (CW) and counterclockwise. FliG, one of the rotor proteins, consists of three domains: N-terminal (FliGN), middle (FliGM), and C-terminal (FliGC). We have identified point mutations in FliGC from Vibrio alginolyticus, which affect the flagellar motility. To understand the molecular mechanisms, we explored the structural and dynamic properties of FliGC from both wild-type and motility-defective mutants. From nuclear magnetic resonance analysis, changes in signal intensities and chemical shifts between wild-type and the CW-biased mutant FliGC are observed in the Cα1-6 domain. Molecular dynamics simulations indicated the conformational dynamics of FliGC at sub-microsecond timescale, but not in the CW-biased mutant. Accordingly, we infer that the dynamic properties of atomic interactions around helix α1 in the Cα1-6 domain of FliGC contribute to ensure the precise regulation of the motor switching.
STRUCTURE 25(10), 1540-1548.e3, 2017-10-03