The control of actin nucleotide exchange by thymosinβ4 and profilin. A potential regulatory mechanism for actin polymerization in cells

P. J. Goldschmidt-Clermont, M. I. Furman, D. Wachsstock, D. Safer, V. T. Nachmias, T. D. Pollard

Research output: Contribution to journalArticlepeer-review

225 Scopus citations


We present evidence for a new mechanism by which two major actin monomer binding proteins, thymosinβ4 and profilin, may control the rate and the extent of actin polymerization in cells. Both proteins bind actin monomers transiently with a stoichiometry of 1:1. When bound to actin, thymosinβ4 strongly inhibits the exchange of the nucleotide bound to actin by blocking its dissociation, while profilin catalytically promotes nucleotide exchange. Because both proteins exchange rapidly between actin molecules, low concentrations of profilin can overcome the inhibitory effects of high concentrations of thymosinβ4 on the nucleotide exchange. These reactions may allow variations in profilin concentration (which may be regulated by membrane polyphosphoinositide metabolism) to control the ratio of ATP-actin to ADP-actin. Because ATP-actin subunits polymerize more readily than ADP-actin subunits, this ratio may play a key regulatory role in the assembly of cellular actin structures, particularly under circumstances of rapid filament turnover.

Original languageEnglish (US)
Pages (from-to)1015-1024
Number of pages10
JournalMolecular biology of the cell
Issue number9
StatePublished - 1992

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology


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