Crystallization and functional analysis of a soluble deglycosylated form of the human costimulatory molecule B7-1
Davis SJ, Ikemizu S, Collins AV, Fennelly JA, Harlos K, Jones EY, Stuart DI. (2001), Acta Crystallogr D Biol Crystallogr. 57, 605-8
The interactions of B7-1 with CD28 and CTLA-4 modulate the course of human immune responses, making B7-1 an important target for developing structure-based therapeutics. B7-1 is, however, one of the most heavily glycosylated proteins found at the leukocyte cell surface, complicating the structural analysis of this molecule. Methods for the production, crystallization and selenomethionine labelling of a soluble deglycosylated form of this molecule are described. The protein readily forms both tetragonal plate and bipyramidal crystals belonging to space groups I4(1)22, with unit-cell parameters a = b = 56.9, c = 298.7 A, and P4(1)22 (or P4(3)22), with unit-cell parameters a = b = 89.0, c = 261.9 A, respectively. The I4(1)22 and primitive crystal forms diffract to 2.7 and 3.5 A, respectively. Surface plasmon resonance-based assays indicate that the ligand-binding properties of sB7-1 are unaffected by deglycosylation. Since none of the methods relied on any special structural properties of sB7-1, it is proposed that this novel combination of procedures could in principle be adapted to the systematic analysis of many other glycoproteins of structural or functional interest.
Key figure: Crystals of human sB7-1
(a) Initial crystals of deglycosylated sB7-1 grown prior to removal of the hexahistidine tag. (b) Body-centred (bc) and primitive (p) crystals of SeMet-labelled sB7-1 used for multiple wavelength anomalous dispersion data collection at the ESRF.