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Molecular mechanism of Ena/VASP‐mediated actin‐filament elongation
Author(s) -
Breitsprecher Dennis,
Kiesewetter Antje K,
Linkner Joern,
Vinzenz Marlene,
Stradal Theresia E B,
Small John Victor,
Curth Ute,
Dickinson Richard B,
Faix Jan
Publication year - 2011
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/emboj.2010.348
Subject(s) - biology , protein filament , mechanism (biology) , actin , elongation , microbiology and biotechnology , cytoskeleton , biophysics , genetics , physics , materials science , cell , ultimate tensile strength , metallurgy , quantum mechanics
Ena/VASP proteins are implicated in a variety of fundamental cellular processes including axon guidance and cell migration. In vitro , they enhance elongation of actin filaments, but at rates differing in nearly an order of magnitude according to species, raising questions about the molecular determinants of rate control. Chimeras from fast and slow elongating VASP proteins were generated and their ability to promote actin polymerization and to bind G‐actin was assessed. By in vitro TIRF microscopy as well as thermodynamic and kinetic analyses, we show that the velocity of VASP‐mediated filament elongation depends on G‐actin recruitment by the WASP homology 2 motif. Comparison of the experimentally observed elongation rates with a quantitative mathematical model moreover revealed that Ena/VASP‐mediated filament elongation displays a saturation dependence on the actin monomer concentration, implying that Ena/VASP proteins, independent of species, are fully saturated with actin in vivo and generally act as potent filament elongators. Moreover, our data showed that spontaneous addition of monomers does not occur during processive VASP‐mediated filament elongation on surfaces, suggesting that most filament formation in cells is actively controlled.