A new conformation of the integrin-binding fragment of human VCAM-1 crystallizes in a highly hydrated packing arrangement

An X-ray crystal structure of two N-terminal integrin-binding IgSF domains of human VCAM-1 is reported. This new crystal form shows an unusual and highly hydrated packing arrangement in which over 80% of the crystal is occupied by solvent. The relative orientations of the two domains adopt a new intermediate conformation. The tilt angle between the two domains is 19.4°, compared with other related structures that have tilt angles ranging from 7.3 to 39.9°. An analysis of the torsion angles shows that residues Ile88, Tyr89, Ser90, Pro92 and Glu96 play a major role in defining the interdomain conformations.