INTERACTION OF ANNEXIN-IV AND ANNEXIN-VI WITH ATP - AN ALTERNATIVE MECHANISM BY WHICH A CELLULAR FUNCTION OF THESE CALCIUM-BINDING AND MEMBRANE-BINDING PROTEINS IS REGULATED

Annexin VI from porcine liver can be photoaffinity-labeled with 8-azid o-[gamma-P-32]ATP in a concentration-dependent, saturable manner. The extent of labeling varied with the concentration of calcium. The disso ciation constant for the nucleotide was found to be in the range repor ted for ATP-binding proteins. The ATP analog, 2'-(or 3')-O-(2,4,6-trin itrophenyl)adenosine 5'-triphosphate, also bound to AnxVI, as indicate d by shift in its fluorescence spectra in the presence of protein. Any significant 8-azido-ATP or TNP-ATP binding was not observed with AnxI V. ATP modulated the binding of AnxVI to erythrocyte membrane and incr eased the Ca2+ concentration required for half-maximal binding of AnxV I to F-actin. (C) 1997 Federation of European Biochemical Societies.