Crystals of the β-subunit of bovine luteinizing hormone and indicators for the involvement of proteolysis in protein crystallization

The beta-subunit of luteinizing hormone (LH), the subunit responsible for the physiological response, has been crystallized beginning with the intact alphabeta-heterodimeric hormone purified from bovine pituitary glands. The crystals were grown at 310 K in the presence of neutral detergents along with trypsin. The tetragonal bipyramidal crystals diffract to 3 A resolution and belong to space group I4(1)22, with unit-cell parameters a = b = 57, c = 207 A. It is noted that proteins exposed to proteases sometimes yield products that crystallize better than the native molecule and that the beta-subunit of LH represents yet another example. Some indicators of when proteolysis may be a factor in crystallization, as well as some consequences, are described.