Crystallization and preliminary X-ray diffraction analysis of the extracellular domain of the cell surface antigen CD38 complexed with ganglioside

The cell surface antigen CD38 is a multifunctional ectoenzyme that acts as an NAD(+) glycohydrolase, an ADP-ribosyl cyclase, and also a cyclic ADP-rib ose hydrolase, The extracellular catalytic domain of CD38 was expressed as a fusion protein with maltose-binding protein, and was crystallized in the complex with;a ganglioside, G(T1b), one of the possible physiological inhib itors of this ectoenzyme, Two different crystal forms were obtained using t he hanging-drop vapor diffusion method with PEG 10,000 as the precipitant. One form diffracted up to 2.4 Angstrom resolution with synchrotron radiatio n at 100 K,but suffered serious X-ray damage. It belongs to the space group P2(1)2(1)2(1) with unit-cell parameters of a = 47.9, b = 94.9, c = 125.2 A ngstrom. The other form is a thin plate, but the data sets were successfull y collected up to 2.4 Angstrom resolution by use of synchrotron radiation a t 100 K. The crystals belong to the space group P2(1) with unit-cell parame ters of a = 57.4, b = 51.2, c = 101.1 Angstrom, and beta = 97.0 degrees, an d contain one molecule per asymmetric unit with a VIM value of 2.05 Angstro m(3)/Da.