Crystallization and preliminary X-ray diffraction characterisation of both a native and selenomethionyl VLA-4 binding fragment of VCAM-1

Soluble fragments of the extracellular region of vascular cell adhesion molecule 1 (VCBM-1) expressed in Escherichia coli retain functional adhesive activity. An integrin (VLA-4) binding fragment consisting of the N-terminal two immunoglobulin-like domains (VCAM-d1,2) has been crystallized. The crystals belong to space group P2₁2₁2₁ with cell dimensions of a = 52.7 Å, b = 66.5 Å, c = 113.2 Å and contain two molecules in the crystallographic asymmetric unit. A batch of protein produced in the standard E. coli strain (HW1110), but grown in the presence of selenomethionine enriched media, showed 85% incorporation of selenium in place of sulphur at methionine residues. The selenomethionyl VCAM-d1,2 was crystallized by microseeding techniques initially using the native crystals for nucleation. Both native and selenomethiongrl crystals diffract X-rays to a minimum Bragg spacing of 1.8 Å.