Biochemical and Biophysical Research Communications, Vol.365, No.4, 746-750, 2008
Cross-talk among structural domains of human DBP upon binding 25-hydroxyvitamin D
Serum vitamin D-binding protein (DBP) is structurally very similar to serum albumin (ALB); both have three distinct structural domains and high cysteine-content. Yet, functionally they are very different. DBP possesses high affinity for vitamin D metabolites and G-actin, but ALB does not. It has been suggested that there may be cross-talk among the domains so that binding of one ligand may influence the binding of others. In this study we have employed 2-p-toluidinyl-6-sulfonate (TNS), a reporter molecule that fluoresces upon binding to hydrophobic pockets of DBP. We observed that recombinant domain III possesses strong binding for TNS, which is not influenced by 25-hydroxyvitamin D-3 (25-OH-D-3) yet TNS fluorescence of the whole protein is quenched by 25-OH-D-3. These results provide a direct evidence of cross-talk among the structural domains of DBP. (c) 2007 Elsevier Inc. All rights reserved.