Covalent complexes formed between plasma gelsolin and actin with a zero-length cross-linking compound.
Actin and plasma gelsolin were covalently cross-linked with the zero-length cross-linker 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide. Two major intermolecularly linked products were identified on polyacrylamide gels. By use of 14C-labeled actin and 125I-labeled gelsolin, these were shown to be the 1:1 and 2:1 complexes of actin with gelsolin, respectively. The higher molecular weight complex predominated under all conditions tested including the presence and absence of Ca2+. In titration experiments in which actin at different concentrations was reacted with a fixed concentration of gelsolin, end points were obtained for the formation of both cross-linked species at about two actins per gelsolin, implying that a 2:1 noncovalent complex is cross-linked. In 0.1 mM Ca2+, the extent of cross-linking was independent of protein concentration down to 50 nM gelsolin. At low Ca2+ concentrations (less than 10(-8)M), the extent of cross-linking was very much reduced at micromolar gelsolin and fell to zero at about 100 nM gelsolin. The binding of actin to gelsolin to give a cross-linkable complex is therefore very strong at 0.1 mM Ca2+ but much weaker at low Ca2+ concentrations.
D000199:Actins / Q000378:metabolism*; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002234:Carbodiimides / Q000378:metabolism*; D002250:Carbon Radioisotopes; D005022:Ethyldimethylaminopropyl Carbodiimide / Q000378:metabolism*; D018260:Gelsolin; D007700:Kinetics; D008840:Microfilament Proteins / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D011817:Rabbits; D013552:Swine
D000199:Actins; D002135:Calcium-Binding Proteins; D002234:Carbodiimides; D002250:Carbon Radioisotopes; D018260:Gelsolin; D008840:Microfilament Proteins; D005022:Ethyldimethylaminopropyl Carbodiimide