Crystallization and preliminary X-ray diffraction analysis of boar seminal plasma spermadhesin PSP-I/PSP-II, a heterodimer of two CUB domains

Boar spermadhesin PSP-I/PSP-II (M(r) 29 000-30 000), a non-covalent heterodimer of two CUB domains, was crystallized in two crystal forms, Complete diffraction data sets for hexagonal (space group P6(1,5)22) and trigonal (space group P3(1,2)21) crystals have been collected up to 2.9 and 2.5 Angstrom resolution, respectively. Cell constants of the hexagonal and trigonal crystal forms are a=b=87.2 Angstrom, c=152.4 Angstrom, and a=b=96.2 Angstrom, c=70.8 Angstrom, respectively. The calculated packing parameters (V-m) are 2.8 and 3.2 Angstrom(3)/Da for the hexagonal and trigonal crystal forms, respectively, indicating that, in both cases, the asymmetric unit is constituted by one PSP-I/PSP-II heterodimer, This paper reports the first crystals of a protein built up by a CUB domain architecture.