Group-specific component (vitamin D binding protein) prevents the interaction between G-actin and profilin

Biochemistry. 1986 Oct 21;25(21):6467-72. doi: 10.1021/bi00369a019.


Profilin purified from human platelets formed a 1:1 molar ratio complex with rabbit skeletal muscle G-actin but was displaced by purified serum Gc (vitamin D binding protein) in a dose-dependent fashion as assessed by chromatography and ultrafiltration. This suggested that Gc and profilin competed for the same binding area on G-actin, with Gc-G-actin complexes being more stable than profilin-G-actin complexes in vitro. The binding domain for Gc on G-actin was localized to a 16,000-Da C-terminal fragment of G-actin generated by Staphylococcus aureus V8 protease, as judged by comigration on two-dimensional electrophoresis and also by overlaying electrophoresis gels with 125I-Gc. Previous studies have reported that residues 374 and 375 of G-actin are essential for binding of profilin. In this study, experiments involving tryptic removal of Cys-374 labeled with the fluorescent probe N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl)-ethylenediamine showed that these C-terminal amino acids were not necessary for interaction with Gc.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / metabolism*
  • Animals
  • Blood Platelets / metabolism
  • Contractile Proteins*
  • Electrophoresis, Polyacrylamide Gel
  • Humans
  • Kinetics
  • Microfilament Proteins*
  • Molecular Weight
  • Muscles / metabolism
  • Profilins
  • Proteins / isolation & purification
  • Proteins / metabolism*
  • Rabbits
  • Ultrafiltration
  • Vitamin D-Binding Protein / pharmacology*


  • Actins
  • Contractile Proteins
  • Microfilament Proteins
  • PFN1 protein, human
  • Profilins
  • Proteins
  • Vitamin D-Binding Protein