How profilin promotes actin filament assembly in the presence of thymosin beta 4

Cell. 1993 Dec 3;75(5):1007-14. doi: 10.1016/0092-8674(93)90544-z.


The role of profilin in the regulation of actin assembly has been reexamined. The affinity of profilin for ATP-actin appears 10-fold higher than previously thought. In the presence of ATP, the participation of the profilin-actin complex to filament elongation at the barbed end is linked to a decrease in the steady-state concentration of globular actin. This surprising effect is made possible by the involvement of the irreversible ATP hydrolysis accompanying actin polymerization. As a consequence, in the presence of thymosin beta 4 (T beta 4), low amounts of profilin promote extensive actin assembly off of the pool of actin-T beta 4 complex. When barbed ends are capped, profilin simply sequesters globular actin. A model is proposed for the function of profilin in actin-based motility.

MeSH terms

  • Actin Cytoskeleton / metabolism
  • Actin Cytoskeleton / ultrastructure*
  • Actins / metabolism*
  • Actins / ultrastructure
  • Adenosine Diphosphate / metabolism
  • Adenosine Triphosphate / metabolism
  • Animals
  • Contractile Proteins*
  • Gelsolin / metabolism
  • Humans
  • In Vitro Techniques
  • Kinetics
  • Microfilament Proteins / metabolism
  • Microfilament Proteins / physiology*
  • Profilins
  • Sheep
  • Thymosin / pharmacology


  • Actins
  • Contractile Proteins
  • Gelsolin
  • Microfilament Proteins
  • PFN1 protein, human
  • Profilins
  • thymosin beta(4)
  • Thymosin
  • Adenosine Diphosphate
  • Adenosine Triphosphate