CRYSTALLIZATION AND PRELIMINARY-X-RAY DIFFRACTION CHARACTERIZATION OFBOTH A NATIVE AND SELENOMETHIONYL VLA-4 BINDING FRAGMENT OF VCAM-1

Soluble fragments of the extracellular region of vascular cell adhesio n molecule 1 (VCAM-1) expressed in Escherichia coli retain functional adhesive activity An integrin (VLA-4) binding fragment consisting of t he N-terminal two immunoglobulin-like domains (VCAM-d1,2) has been cry stallized. The crystals belong to space group P2(1)2(1)2(1) with cell dimensions of 52.7 Angstrom b = 66.5 Angstrom, c = 113.2 Angstrom and contain two molecules in the crystallographic asymmetric unit. A batch of protein produced in the standard E. coli strain (HW1110), but grow n in the presence of selenomethionine enriched media, showed 85% incor poration of selenium in place of sulphur at methionine residues. The s elenomethionyl VCAM-d1,2 was crystallized by microseeding techniques i nitially using the native crystals for nucleation. Both native and sel enomethionyl crystals diffract X-rays to a minimum Bragg spacing of 1. 8 Angstrom.