NMR ANALYSES OF THE INTERACTIONS OF HUMAN ANNEXIN-I WITH ATP, CA2+, AND MG2+

Human annesin I is a member of the annesin family of calcium-dependent phospholipid binding proteins. The structure of an N-terminally trunc ated human annesin I (Delta-annexin I) and its interactions with Ca2+, Mg2+, and ATP were studied at the atomic level using nuclear magnetic resonance (NMR) spectroscopy. Since Delta-annexin I is a large protei n, with a molecular vi eight of 35 kDa, a site-specific (carbonyl-C-13 , amide-N-15) labeling technique mas used to determine the interaction sites of Delta-annexin I with Ca2+, Mg2+, and ATP. The C-13 NMR study focused on the carbonyl carbon resonances of the histidine residues o f Delta-annexin I. We found that ATP binds to Delta-annexin I, and tha t the ATP binding site is located in the I-domain of annexin I. We als o found that histidine-52 is involved in that site, and that the bindi ng ratio of ATP to Delta-annexin I is 1:1. (C) 1998 Federation of Euro pean Biochemical Societies.