CONFORMATIONAL CHANGES IN ACTIN FILAMENTS INDUCED BY FORMIN BINDING TO THE BARBED END
Gábor Papp 1, Beáta Bugyi 1, Zoltán Ujfalusi 1, Szilvia Barkó 1, Gábor Hild 1, Béla Somogyi 1 and Miklós Nyitrai 2*
1 University of Pécs, Department of Biophysics
2 University of Pécs
* To whom correspondence should be addressed. E-mail: miklos.nyitrai{at}aok.pte.hu.
Submitted on April 24, 2006
Revised on May 18, 2006
Accepted on 12 June 2006
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Abstract |
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Formins bind actin filaments and play essential roles in the regulation of the actin cytoskeleton. In this work we described details of the formin induced conformational changes in actin filaments by fluorescence lifetime and anisotropy decay experiments. The results showed that the binding of the FH2 domain of a mammalian formin (mouse mDia1) to actin filaments resulted in a less rigid protein structure in the microenvironment of the Cys374 of actin, in the weakening of the interactions between neighbouring actin protomers and in a greater overall flexibility of the actin filaments. The formin effect was smaller at greater ionic strength. The results showed that formin binding to the barbed end of actin filaments was responsible for the increase of the flexibility of actin filaments. One formin dimer could affect the dynamic properties of an entire filament. Analyses of the results obtained at various formin : actin concentration ratios indicated that at least 160 actin protomers were affected by the binding of a single formin dimer to the barbed end of a filament.
Key Words:
actin cytoskeleton, allosteric interactions, fluorescence spectroscopy, proteins, salt dependence, time-resolved fluorescence
