Crystallization of BMP receptor type IA bound to the antibody Fab fragment AbD1556.

An antibody Fab fragment, AbD1556, was selected against the extracellular domain of BMP receptor type IA, which blocks the binding of BMP-2 to BMPR-IA and thereby neutralizes BMP-2 activity. To study the mechanism by which BMPR-IA is recognized and bound by the Fab fragment, the complex of AbD1556 bound to BMPR-IA was prepared and crystallized. Crystals of this binary complex belonged to the monoclinic space group P2(1), with unit-cell parameters a=89.32, b=129.25, c=100.24 A, beta=92.27 degrees.