title: The interaction of calmodulin with human and avian spectrin.
abstract: An air-driven ultracentrifuge was used to investigate the calcium-dependent interaction of 125I-calmodulin with human and avian spectrins. The equilibrium constants (Ka) for the interaction between calmodulin and human spectrin dimer and tetramer under non-denaturing conditions were estimated to be 4.6 X 10(4) M-1 and 7.3 X 10(4) M-1, respectively. The denaturation of human spectrin by urea (5 M) increased the Ka for calmodulin to 4.6 X 10(5) M-1. The value of Ka for the interaction of calmodulin with avian spectrin dimer under non-denaturing conditions was 5.1 X 10(5) M-1. A bifunctional reagent cross-linked both avian spectrin and human spectrin to calmodulin in a calcium-dependent manner.
mesh_terms: D000251:Adenosine Triphosphatases / Q000097:blood; D000818:Animals; D001717:Birds; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002147:Calmodulin / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000201:enzymology; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D008274:Magnesium / Q000494:pharmacology; D011485:Protein Binding; D011489:Protein Denaturation; D013045:Species Specificity; D013049:Spectrin / Q000378:metabolism*; D014508:Urea / Q000494:pharmacology
chemical_list: D002147:Calmodulin; D046911:Macromolecular Substances; D013049:Spectrin; D014508:Urea; D000251:Adenosine Triphosphatases; D008274:Magnesium; D002118:Calcium