ALUMINUM COORDINATION TO CALMODULIN - THERMODYNAMIC AND KINETIC ASPECTS

Calmodulin is an acidic, Ca(II)-binding protein (about 17 000 d) which plays a key role in regulating a broad spectrum of target enzymes in eukaryotic cells. Within each lobe of the dumbbell-shaped molecule the re are two adjacent Ca(II)-binding domains, which form a single cooper ative unit. Hydrophobic forces are crucial for interfacing the Ca(II)- activated regulatory protein with its target enzyme. Presumably not in volving the four specific Ca(II)-binding domains on calmodulin, bindin g of Al(III) to calmodulin generates considerable dehydration entropie s. Al(III)-triggered changes in the alpha-helix content of calmodulin are involved in the mismatch between calmodulin and its target protein . By altering calmodulin's internal dynamics, Al(III) apparently inter feres with the proteins capacity to search out conformational substate s suitable for proper docking with a specific target protein.