Multiple kinetic states for the flagellar motor switch

S. C. Kuo, D. E. Koshland

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


By means of a computerized video processing system, the flagellar motors of Escherichia coli were shown to have multiple kinetic states for each rotational direction. High-resolution analysis of flagellar motors revealed new kinetic states both in wild-type cells and in a strain deleted of other signal-transducing genes to which CheY had been introduced. This strain, RP1091, retained residual kinase activity that could phosphorylate CheY, complicating the biochemical identification of certain kinetic states. The behavioral effects of CheY on single flagellar motors was ultrasensitive, with an apparent Hill coefficient of 5.5 ± 1.9 (SD) and a half-maximal effect at 10.1 ± 0.5 (SD) μM CheY. Based on the CheY concentration dependence, a two-state model is clearly excluded, even for the simpler system of CheY-induced rotational reversals in the deletion strain. The data are best described by a four-state model, with two clockwise and two counterclockwise states.

Original languageEnglish (US)
Pages (from-to)6279-6287
Number of pages9
JournalJournal of bacteriology
Issue number11
StatePublished - 1989
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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