Purification,characterization and crystallization in two crystal forms of bovine cyclophilin 40

The purification and crystallization of two different crystal forms of the two-domain protein bovine cyclophilin 40 is reported. Tetragonal crystals g rown in methyl pentanediol belong to space group P4(2)22 with unit-cell par ameters a = 94.5, c = 118.3 Angstrom. Long thin needles grown from PEG belo ng to space group C2 with unit-cell parameters a = 125.71, b = 47.3, c = 74 .6 Angstrom, beta = 93.90 degrees. The N-terminal 170 amino acids have sign ificant homology with the well characterized human cyclophilin A. The C-ter minal domain is largely made up of three copies of the tetratricopeptide re peat motif thought to be involved in mediating protein-protein interactions . Cyclophilins are frequently found as domains in larger multidomain protei ns. To date, only X-ray structures of single-domain cyclophilins have been reported, and this work provides the first example of the purification and crystallization of a larger protein containing a cyclophilin domain.