Conformational Spread as a Mechanism for Cooperativity in the Bacterial Flagellar Switch

Fan Bai, Richard W. Branch, Dan V. Nicolau, Teuta Pilizota, Bradley C. Steel, Philip K. Maini, Richard M. Berry

Research output: Contribution to journalArticlepeer-review


The bacterial flagellar switch that controls the direction of flagellar rotation during chemotaxis has a highly cooperative response. This has previously been understood in terms of the classic two-state, concerted model of allosteric regulation. Here, we used high-resolution optical microscopy to observe switching of single motors and uncover the stochastic multistate nature of the switch. Our observations are in detailed quantitative agreement with a recent general model of allosteric cooperativity that exhibits conformational spread-the stochastic growth and shrinkage of domains of adjacent subunits sharing a particular conformational state. We expect that conformational spread will be important in explaining cooperativity in other large signaling complexes.

Original languageEnglish
Pages (from-to)685-689
Number of pages5
Issue number5966
Publication statusPublished - 5 Feb 2010


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