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 P2(1)2(1)2(1) space group (a=65.6 A, b=117.5 A, c=145.8 A) with two protein molecules per asymmetric unit. A complete SAD data set from Se-Methionine derived crystal (3.2 A) has been collected to solve the structure.