PRELIMINARY CRYSTALLOGRAPHIC DATA FOR AN FAB TO THE MELANOMA-ASSOCIATED GD2 GANGLIOSIDE, AND THE PURIFICATION OF A SOLUBLE FORM OF THIS ANTIGEN

An Fab fragment from a monoclonal antibody (ME36.1) to the melanoma-as sociated GD2 ganglioside has been purified and crystallized in space g roup P2(1) with unit-cell dimensions a = 37.6, b = 94.1, c = 67.4 Angs trom, beta = 101.0 degrees. The crystals, which grow to a size of up t o 0.6 x 0.5 x 0.3 mm, diffract to 2.5 Angstrom, and native data have b een collected to 2.8 Angstrom, resolution. The crystal density is 1.22 g ml(-1) indicating one molecule of 48 kDa per asymmetric unit and a solvent content of 51%. A soluble form of the carbohydrate was obtaine d from the scarce GD2 glycolipid by enzymatic digestion with ceramide- glycanase. Small co-crystals of the Fab-GD2 complex have been obtained . As ME36.1 has been used in immunotherapy to treat malignant melanoma , knowledge of its interactions with the ganglioside could increase th e efficacy of these treatments.