Fig. 1: Binding of CheY-P to the motor increases with the number of bound stator units. | Nature Communications

Fig. 1: Binding of CheY-P to the motor increases with the number of bound stator units.

From: Mechanosensitive recruitment of stator units promotes binding of the response regulator CheY-P to the flagellar motor

Fig. 1

a We monitored the rotation of tethered cells simultaneously in the TIRF and phase channels. The fluorescent moieties (CheY-EYFP) were visible in the evanescent field as they bound to the motor: The top row shows a time series of TIRF images for a single tethered cell. The arrow points to CheY-P bound to the motor. The corresponding phase contrast images are shown in the bottom row. The ⨯ shows the point of tethering around which the cell rotates. b The intensity of CheY-P localized around each motor was quantitatively estimated from the TIRF images (see Methods). The probability-density estimates are indicated for a strain carrying functional stators (MotAB+ strain, black curve, n = 50 independent motors) and a strain lacking stator proteins (ΔmotAB strain, red curve, n = 48 independent motors). The difference in the mean intensities in the two strains was significant (***p-value = 1.3 × 10−7, <0.001). The mean number of CheY-P molecules bound to the motor in the absence of stator units was lower than that in the presence of stators units. c We compared CheY-EYFP binding to the motors in the ΔmotAB strain transformed with a plasmid encoding MotA and MotB with that in a ΔmotAB strain transformed with an empty plasmid. The strain lacking MotA-MotB (red curve, n = 108 independent motors) had significantly lower intensities (***p-value = 1.7 × 10−5, <0.001) than the strain expressing MotA-MotB (black curve, n = 46 independent motors). d We measured the localization of FliM-EYFP-FliM in each tethered cell. The difference in the mean intensities in the motors of a strain carrying functional stators (blue curve, n = 75 independent motors) and a strain lacking stator proteins (magenta curve, n = 115 independent motors) was not statistically significant (ns, p-value > 0.05). e Tethered cells were stalled by obstructing the rotation with optically trapped beads. The difference in the mean CheY-EYFP intensities in rotating cells (black curve, n = 86 independent motors) and stalled cells (red curve, n = 36 independent motors) was not statistically significant (ns, p-value > 0.05). Source data are provided as a Source Data file.

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