title: High-resolution crystal structures of alternate forms of the human CD44 hyaluronan-binding domain reveal a site for protein interaction.
abstract: Two new crystal structures of the extracellular hyaluronan-binding domain of human CD44 are described at high resolution. A hexagonal crystal form at 1.60 Å resolution and a monoclinic form at 1.08 Å resolution both have two molecules in the asymmetric unit arranged about a similar noncrystallographic twofold axis of symmetry. These structures are compared with those previously reported at 2.20 Å resolution to show that the fold is quite resistant to structural deformation in different crystal environments. Unexpectedly, a short peptide is found in the monoclinic crystals at a site remote from the known hyaluronan-binding groove. The peptide with a valine at the carboxy-terminus must have co-purified from the bacterial expression host and binds on the opposite side of the domain from the known hyaluronan-binding groove. This opportunistic binding may identify a site of interaction used as CD44 assembles with other proteins to accomplish effective signaling regarding changes to the extracellular environment.
authors.affiliation: Department of Medicinal Chemistry, University of Minnesota, 308 Harvard Street SE, Minneapolis, MN 55455, USA.
authors.forename: Li-Kai
authors.initials: LK
authors.lastname: Liu
authors.affiliation: Department of Medicinal Chemistry, University of Minnesota, 308 Harvard Street SE, Minneapolis, MN 55455, USA.
authors.forename: Barry
authors.initials: B
authors.lastname: Finzel
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D017931:DNA Primers; D006801:Humans; D018960:Hyaluronan Receptors / Q000737:chemistry*; D006820:Hyaluronic Acid / Q000737:chemistry*; D008958:Models, Molecular; D011506:Proteins / Q000737:chemistry*
chemical_list: D017931:DNA Primers; D018960:Hyaluronan Receptors; D011506:Proteins; D006820:Hyaluronic Acid
keywords: CD44; hyaluronan-binding domain