Purification, crystallization and preliminary crystallographic studies of C-terminal RNA recognition motif (RRM-3) of human ELAV-type RNA-binding protein 3 (ETR-3)

Human embryonically lethal abnormal vision (ELAV)-type RNA-binding protein 3 (ETR-3) has been implicated in many aspects of RNA-processing events including alternative splicing, stability, editing and translation. RNA recognition motif 3 (RRM-3) is an independent C-terminal RNA-binding domain of ETR-3 that preferentially binds to UG-rich repeats of the nuclear or cytoplasmic pre-mRNA, and along with the other domains mediates the inclusion of cardiac troponin T (c-TNT) exon 5 in embryonic muscle, which is otherwise excluded in the adult. In the present study, RRM-3 was cloned, overexpressed, purified and crystallized by the hanging-drop vapour-diffusion method. The crystals diffracted to 3 angstrom resolution at the home source and belonged to space group P2(1)3, with unit-cell parameters a = b = c = 118.5 angstrom, alpha = beta = gamma = 90 degrees. There were two molecules of RRM-3 in the asymmetric unit and the calculated Matthews coefficient (V-M) was 6.35 angstrom(3) Da(-1), with a solvent content of 80.62%. Initial phases were determined by molecular replacement.