Fluorescence investigations of calmodulin hydrophobic sites.
Calmodulin activation of target enzymes depends on the interaction between calmodulin hydrophobic regions and some enzyme areas. The Ca2+ induced exposure of calmodulin hydrophobic sites was studied by means of 2-p-toluidinylnaphthalene-6-sulfonate, a fluorescent probe. Scatchard and Job plots showed that the calmodulin-Ca42+ complex bound two molecules of this hydrophobic probe, with KD congruent to 1.4 X 10(-4) M. These sites are not totally exposed until calmodulin has bound four Ca2+ per molecule, so the conformational change is not over before the four specific Ca2+ - binding sites are saturated with Ca2+.
D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases / Q000378:metabolism; D000818:Animals; D001011:Aorta / Q000201:enzymology; D001921:Brain; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D007700:Kinetics; D013050:Spectrometry, Fluorescence / Q000379:methods
D002147:Calmodulin; D015087:2',3'-Cyclic-Nucleotide Phosphodiesterases; D002118:Calcium