Crystal structures of the ligand-binding region of uPARAP: effect of calcium ion binding

We report the crystal structures of the first four domains of uPARAP (also named the ligand-binding region, LBR) at pH 7.4 in Ca2+-bound and Ca2+-free forms. The first domain (cysteine-rich or CysR domain) folds into a new and unique conformation different from the β-trefoil fold of typical CysR domains. The so-called long loop regions (LLRs) of the C-type lectin-like domain (CTLD) 1 and 2 (the third and fourth domain) mediate the direct contacts between these domains. These LLRs undergo a Ca2+-dependent conformational change, and this is likely to be the key structural determinant affecting the overall conformation of uPARAP. Our results provide a molecular mechanism to support the structural flexibility of uPARAP, and shed light on the structural flexibility of other members of the MR family.
Source: Biochemical Journal - Category: Biochemistry Authors: Tags: Research articles Source Type: research