Crystallization and preliminary crystallographic study of b0220, an `ORFan' protein of unknown function from Escherichia coli

Newly sequenced microbial genomes continue to reveal up to 50% functionally uncharacterized `anonymous' genes. A significant fraction of these anonymous ORFs does not exhibit any sequence similarity to any protein in the databases and constitutes a set of unique sequences, denoted `ORFans'. The structure determination of ORFan proteins is both of evolutionary and functional interest. Here, the first crystallization of an Escherichia coli ORFan gene product, the 157 amino-acid b0220 protein, is reported. The crystals belong to the trigonal space group P3 or P3₁, with unit-cell parameters a = b = 47.2, c = 88.4 Å. There are two molecules in the asymetric unit. Frozen crystals diffract to 1.6 Å resolution using synchrotron radiation. Phasing was performed using multiwavelength anomalous dispersion (MAD) on the selenomethionine-substituted b0220 protein.