PMID: 25195884
Liu LK, Finzel B
High-resolution crystal structures of alternate forms of the human CD44 hyaluronan-binding domain reveal a site for protein interaction.
Acta Crystallogr F Struct Biol Commun. 2014 Sep 1;70(Pt 9):1155-61. doi:, 10.1107/S2053230X14015532. Epub 2014 Aug 29.
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 A resolution and a monoclinic form at 1.08 A 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 A 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.