The Role of the FH1 Domain and Profilin in Formin-Mediated Actin-Filament Elongation and Nucleation

Abstract

On page R15 of this essay, the following sentence contains a problematic citation: ''This circular interpretation has been taken to such an extreme that some recent studies now interpret any fMRI response in areas vPM and aIPS-for example, fMRI responses while observing moving shapes [10]-as being due to mirror neuron activity.''The citation of this particular study alone ([10], Wheatley et al.) was a mistake because although the authors of the study offered one interpretation of the fMRI activity in areas vPM and aIPS as arising from mirror neuron activity, they also offered an alternative interpretation that was overlooked by the authors of this essay. The cited study should not have been singled out, and the authors of this essay regret this error.

A cooperative jack model of random coil‐to‐elongation transition of the FH1 domain by profilin binding explains formin motor behavior in actin polymerization

“…Both the acceleration effect of formin motor on actin filament assembly and the conformational elongation of FH1 domain depend on the number of available profilin binding sites in FH1 domain [18]. Furthermore, there is a decrease in the contribution of each additional profilin bound site in both accelerating actin filament assembly [18] and elongating the FH1 domain.…”

“…Furthermore, there is a decrease in the contribution of each additional profilin bound site in both accelerating actin filament assembly [18] and elongating the FH1 domain. A cooperative ''jack'' model of random coil-to-elongation transition of the FH1 domain is thus proposed to explain the formin motor behavior in terms of the FH1 conformations in the presence of profilinactins (Fig.…”

“…These models combined with the information gained from crystal structures of the FH2 domain [8,12] improved our understanding of the processive progression of formins along the barbed end of actin filaments. To clarify the acceleration effect of the formin motor during actin assembly, studies so far have found that the acceleration is dependent on the number of profilin binding sites in the FH1 domain [18]. However, due to the disordered nature of the FH1 domain (Fig.…”

ArabidopsisFormin3 Directs the Formation of Actin Cables and Polarized Growth in Pollen Tubes

“…The FH1 domain contains a polyproline stretch, which binds to profilin (actin monomer binding protein) and profilin-actin, while the number of poly-proline repeats is variable among different formins (Kovar et al, 2006). Provided with sufficient amounts of profilin, the rate of barbedend elongation in the presence of formin increases with the increasing number of poly-proline tracks in the FH1 domain (Paul and Pollard, 2008). The FH2 domain contains actin binding sites and acts as a dimer to nucleate new actin filaments (Xu et al, 2004).…”

The effects of formins on the conformation of subdomain 1 in actin filaments

“…The FH2 domain is responsible for the binding to actin and for alteration of the polymerization properties of filaments. The FH1 domain can modulate this effect through interactions with profilin-actin [9][10][11]. Different formins can have other specific properties as they can depolymerise, sever or bundle filamentous actin [9,[12][13][14][15][16].…”