title: Group-specific component (vitamin D binding protein) prevents the interaction between G-actin and profilin.
abstract: 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.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D003285:Contractile Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007700:Kinetics; D008840:Microfilament Proteins; D008970:Molecular Weight; D009132:Muscles / Q000378:metabolism; D051304:Profilins; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits; D014462:Ultrafiltration; D014809:Vitamin D-Binding Protein / Q000494:pharmacology*
chemical_list: D000199:Actins; D003285:Contractile Proteins; D008840:Microfilament Proteins; C495738:PFN1 protein, human; D051304:Profilins; D011506:Proteins; D014809:Vitamin D-Binding Protein