Crystallization and preliminary X-ray diffraction analysis of three EGF domains of EMR2, a 7TM immune-system molecule

Crystals of three epidermal growth-factor-like (EGF) domains of EMR2 (143 residues) have been grown. EMR2 is a member of the EGF-TM7 family of proteins. Different splice variants exist with between three and five consecutive EGF modules linked to a seven-span transmembrane G-protein-coupled receptor. Although its precise function is unknown, EMR2 is highly expressed in immune tissues and has been shown to weakly bind CD55, a complement-system regulator. Here, crystallization of EMR2 in the presence of Ca(2+), Ba(2+) and Sr(2+) ions is reported. A complete data set has been collected from all three crystal types, all of which belong to space group P2(1). An anomalous Patterson map from the Ba(2+) crystal data reveals three Ba(2+) ions bound within the asymmetric unit.