4yi9

Publication Abstract from PubMed

Recoverin (Rv), a small Ca2+-binding protein that inhibits rhodopsin kinase (RK), has four EF hands, two of which are functional (EF2 and EF3). Activation requires Ca2+ in both EF hands, but crystal structures have never been observed with Ca2+ ions in both sites; all previous structures have Ca2+ bound only to EF3. We suspected that this was due to an intermolecular crystal contact between T80 and a surface glutamate (E153) that precluded coordination of a Ca2+ ion in EF2. We constructed the E153A mutant, determined its X-ray crystal structure to 1.2 A resolution, and show that 2 Ca2+ ions are bound, one in EF3 and one in EF2. Additionally, several other residues are shown to adopt conformations in the 2Ca2+-structure not seen previously and not seen in a second structure of the E153A mutant containing Na+ instead of Ca2+ in the EF2 site. The side-chain rearrangements in these residues form a 28 A long allosteric cascade along the surface of the protein connecting the Ca2+-binding site of EF2 with the active-site pocket responsible for binding RK.

Crystal Structure of Recoverin with Calcium Ions Bound to Both Functional EF-Hands.,Kumar RP, Ranaghan MJ, Ganjei AY, Oprian DD Biochemistry. 2015 Nov 19. PMID:26584024^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.