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

• DOI: 10.1126/science.1182105
• Publication Date: 2010-02-17T17:27:22Z
• Authors: Fan Bai; Richard W. Branch; Dan V. Nicolau; Teuta Pilizota; Bradley C. Steel; Philip K. Maini; Richard M. Berry
• Keywords: Models, Molecular; 0301 basic medicine; 570; 0303 health sciences; Binding Sites; Protein Conformation; Escherichia coli Proteins; Molecular Motor Proteins; Membrane Proteins; Methyl-Accepting Chemotaxis Proteins; 540; Models, Biological; Protein Subunits; 03 medical and health sciences; Allosteric Regulation; Bacterial Proteins; Flagella; Escherichia coli; Thermodynamics; Monte Carlo Method; Protein Binding; Signal Transduction

Complex Cooperativity

Cooperativity in multisubunit protein complexes is classically understood in terms of either a concerted model, in which all subunits switch conformation simultaneously, or a sequential model, in which a subunit switches conformation whenever a ligand binds. More recently, a “conformational spread” model has suggested that a conformational coupling between subunits and between subunit and ligand is probabilistic. Using high-resolution optical microscopy,

Bai et al.

(p. 685 ; see the Perspective by

Hilser

) observed multistate switching of the bacterial flagellar switch complex that was previously understood in terms of a concerted allosteric model. The conformational spread model gives quantitative agreement with the data.