Group-Specific Component (Vitamin D Binding Protein) Prevents the Interaction between G-Actin and Profilin

Pascal J. Goldschmidt-Clermont, Eldwin L. Van Alstyne, Joseph R. Dav, David L. Emerson, Andre E. Nel, John Lazarchick, Robert M. Galbraith

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20 Scopus citations


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 16000-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.

Original languageEnglish (US)
Pages (from-to)6467-6472
Number of pages6
Issue number21
StatePublished - Oct 1986
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry


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