Four crystal forms of a Bence‐Jones protein

Four crystal forms have been grown and characterized by X‐ray diffraction of a Bence‐Jones protein collected from the urine of a multiple myeloma patient more than 40 years ago. Closely related tetragonal and orthorhombic forms belonging to space groups P 4 3 2 1 2 and P 2 1 2 1 2 1 , with unit‐cell parameters a  =  b  = 68.7, c = 182.1 and a = 67.7, b = 69.4, c = 87.3 Å, diffract to 1.5 and 1.9 Å, respectively. Two closely related trigonal forms, both belonging to space group P 3 1 21 with unit‐cell parameters a  =  b  = 154.3 Å but differing by a doubling of the c axis, one 46.9 Å and the other 94.0 Å, diffract to 2.9 and 2.6 Å resolution, respectively. The trigonal crystal of short c ‐axis length shows a positive indication of twinning. The trigonal crystal of longer c axis, which appeared only after eight months of incubation at room temperature, is likely to be composed of proteolytically degraded molecules and unlike the other crystal forms contains two entire Bence‐Jones dimers in the asymmetric unit. This latter crystal form may shed some light on the formation of fibrils common to certain storage diseases.