3-DIMENSIONAL STRUCTURE OF RECOVERIN, A CALCIUM SENSOR IN VISION

Recoverin, a recently discovered member of the EF hand superfamily, se rves as a calcium sensor in vision. We report here the crystal structu re of recombinant unmyristoylated recoverin at 1.9 angstrom resolution . The four EF hands of the protein are arranged in a compact array tha t contrasts with the dumbbell shape of calmodulin and troponin C. A ca lcium ion is bound to EF hand 3, while EF hand 2 can bind samarium but not calcium in this crystal form. The other two EF hands have novel s tructural features that prevent or impair calcium binding. A concave h ydrophobic surface formed by EF hands 1 and 2 may participate in the r eadout of calcium signals by recoverin and its homologs.