Mechanism of Actin Filament Pointed-end Capping by Tropomodulin

Overview

Journal Science

Specialty Science

Date 2014 Jul 26

PMID 25061212

Citations 72

Authors

Jampani Nageswara Rao

Yadaiah Madasu

Roberto Dominguez

Affiliations

Soon will be listed here.

Abstract

Proteins that cap the ends of the actin filament are essential regulators of cytoskeleton dynamics. Whereas several proteins cap the rapidly growing barbed end, tropomodulin (Tmod) is the only protein known to cap the slowly growing pointed end. The lack of structural information severely limits our understanding of Tmod's capping mechanism. We describe crystal structures of actin complexes with the unstructured amino-terminal and the leucine-rich repeat carboxy-terminal domains of Tmod. The structures and biochemical analysis of structure-inspired mutants showed that one Tmod molecule interacts with three actin subunits at the pointed end, while also contacting two tropomyosin molecules on each side of the filament. We found that Tmod achieves high-affinity binding through several discrete low-affinity interactions, which suggests a mechanism for controlled subunit exchange at the pointed end.

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