A pentameric form of human serum amyloid P component. Crystallization, X-ray diffraction and neutron scattering studies.

Human serum amyloid P component crystallizes from sodium acetate buffer (pH 5.5) in the presence of calcium and polyethylene glycol 6000, at 4 degrees C. The space group is P2(1) and the cell parameters are a = 69.0 A (1 A = 0.1 nm), b = 99.3 A, c = 96.8 A, beta = 96.1. Density considerations supported by neutron scattering and gel filtration experiments indicate that the species crystallized is pentameric. The orientation of the pentamer 5-fold axis is determined and a crystal packing for the discs is proposed.