J Biol Chem. 2002 Jun 7;277(23):20999-1006. Epub 2002 Apr 03. Erratum in: J Biol Chem 2002 Sep 6;277(36):33529.

[DOI Link]

Polylysine induces an antiparallel actin dimer that nucleates filament assembly: crystal structure at 3.5-A resolution.

Research Service, Malcom Randall Department of Veterans Affairs Medical Center and the University of Florida College of Medicine, Gainesville, Florida 32608, USA. bubbmr@medicine.ufl.edu

An antiparallel actin dimer has been proposed to be an intermediate species during actin filament nucleation. We now show that latrunculin A, a marine natural product that inhibits actin polymerization, arrests polylysine-induced nucleation at the level of an antiparallel dimer, resulting in its accumulation. These dimers, when composed of pyrene-labeled actin subunits, give rise to a fluorescent excimer, permitting detection during polymerization in vitro. We report the crystallographic structure of the polylysine-actin-latrunculin A complex at 3.5-A resolution. The non-crystallographic contact is consistent with a dimeric structure and confirms the antiparallel orientation of its subunits. The crystallographic contacts reveal that the mobile DNase I binding loop of one subunit of a symmetry-related antiparallel actin dimer is partially stabilized in the interface between the two subunits of a second antiparallel dimer. These results provide a potential explanation for the paradoxical nucleation of actin filaments that have exclusively parallel subunits by a dimer containing antiparallel subunits.

PMID: 11932258 [PubMed - indexed for MEDLINE]

This publication is one of the several that describes a structure solved either at the Kasha Laboratory, Institute of Molecular Biophysics or in collaboration with the Institute Faculty. The data used for this structure determination came in full or part from the Macromolecular X-Ray Crystallography Facility.