Article
- The EMBO Journal (2007) 26, 265 - 274
- doi:10.1038/sj.emboj.7601482
Subject Category:
Reversible movement of switch 1 loop of myosin determines actin interaction
Bálint Kintses1, Máté Gyimesi1, David S Pearson2, Michael A Geeves2, Wei Zeng3, Clive R Bagshaw3 and András Málnási-Csizmadia1
- Department of Biochemistry, Eötvös Lorand University, Budapest, Hungary
- Department of Biosciences, University of Kent, Canterbury, Kent, UK
- Department of Biochemistry, University of Leicester, Leicester, UK
Correspondence to:
András Málnási-Csizmadia, Department of Biochemistry, Eötvös Lorand University, Budapest 1117, Hungary. Tel.: +36 1 381 2171; Fax: +36 1 381 2172; E-mail: malna@elte.hu
Received 18 April 2006; Accepted 25 October 2006
Abstract
The conserved switch 1 loop of P-loop NTPases is implicated as a central element that transmits information between the nucleotide-binding pocket and the binding site of the partner proteins. Recent structural studies have identified two states of switch 1 in G-proteins and myosin, but their role in the transduction mechanism has yet to be clarified. Single tryptophan residues were introduced into the switch 1 region of myosin II motor domain and studied by rapid reaction methods. We found that in the presence of MgADP, two states of switch 1 exist in dynamic equilibrium. Actin binding shifts the equilibrium towards one of the MgADP states, whereas ATP strongly favors the other. In the light of electron cryo-microscopic and X-ray crystallographic results, these findings lead to a specific structural model in which the equilibrium constant between the two states of switch 1 is coupled to the strength of the actin–myosin interaction. This has implications for the enzymatic mechanism of G-proteins and possibly P-loop NTPases in general.
Keywords:
- actomyosin interaction,
- G-proteins,
- Mg-binding,
- nucleotide binding,
- tryptophan fluorescence
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