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-associated GD2 ganglioside has been purified and crystallized in space group P2(1) with unit-cell dimensions a = 37.6, b = 94.1, c = 67.4 A, beta = 101.0 degrees. The crystals, which grow to a size of up to 0.6 x 0.5 x 0.3 mm, diffract to 2.5 A and native data have been collected to 2.8 A 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 obtained 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 the efficacy of these treatments.
The Wistar Institute, Philadelphia, Pennsylvania 19104, USA.
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Burnett