Two different crystal forms of sorcin, a penta-EF-hand Ca2+-binding protein

Sorcin is a 198 amino-acid Ca2+-binding protein that belongs to the penta-E F-hand family. Its Ca2+-binding domain (residues 33-198) has been crystalli zed in the absence of Ca2+ in two different crystal forms. Two complete dat a sets have been collected on a synchrotron source under cryocooling condit ions from crystals grown using ammonium sulfate as precipitant: monoclinic crystals in space group C2, with unit-cell parameters a = 130.93, b = 103.8 5, c = 78.55 Angstrom, beta = 118.0 degrees, diffracting to 2.1 Angstrom, a nd tetragonal crystals in space group P42(1)2, with unit-cell parameters a = b = 103.33, c = 79.15, diffracting to 2.7 Angstrom. Crystals were also gr own using PEG 6000 as precipitating agent. They also belong to space group C2, diffract to 2.8 Angstrom and their unit-cell parameters are very simila r to the first form. Structure determination by molecular replacement has b een initiated. Structural information should be useful for elucidating the interaction of sorcin with membrane targets.