A combinatorial approach to crystallization of PX–BAR unit of the human Sorting Nexin 9

Sorting nexins (SNXs) form a family of proteins known to interact with endosomal vesicles and to regulate various steps of vesicle transport. Sorting Nexin 9 (SNX9) is involved in the interface of endocytic, actin polymerizing, and signal transduction events in the cell. Here we report crystallization of the SNX9 PX–BAR domain protein. Initially we used an ordinary protein construct design, and protein crystallization approaches resulted in obtaining granular crystal-like precipitation. SDS–PAGE and MS analysis of the crystal-like precipitation followed by protein construct optimization and using of macro seeding technique resulted in X-ray quality diffracting crystals. The crystals belonged to P212121 space group (a = 65.6 Å, b = 117.5 Å, c = 145.8 Å) with two protein molecules per asymmetric unit. A complete SAD data set from Se-Methionine derived crystal (3.2 Å) has been collected to solve the structure.