Crystallization and characterization of Pumilio: A novel RNA binding protein

Axis determination in early Drosophila embryos is controlled, in part, by r egulation of translation of mRNAs transcribed in maternal cells during ooge nesis. The Pumilio protein is essential in posterior determination, binding to hunchback mRNA in complex with Nanos to suppress hunchback translation. In order to understand the structural basis of RNA binding, Nanos recruitm ent, and translational control, we have crystallized a domain of the Drosop hila Pumilio protein that binds RNA. The crystals belong to the space group P6(3) with unit cell dimensions of a = b = 94.5 Angstrom, c = 228.9 Angstr om, alpha = beta = 90 degrees, gamma = 120 degrees and diffract to 2.6 Angs trom with synchrotron radiation. We show that the purified protein actively binds RNA and is likely to have a novel RNA binding fold due to a very hig h content of alpha -helical secondary structure. (C) 2000 Academic Press.