The a1?1 integrin receptor binds to its main extracellular ligand, collagen, through an inserted domain in its a-subunit called the aI domain (aI). aI contains a metal binding site that allows collagen to coordinate to the domain through a divalent metal ion. Here we report the backbone assignments of the apo and Mg2+ bound state of the isolated human a1I and the chemical shift changes resulting from metal coordination. ? 2013 Springer Science+Business Media Dordrecht.