Cross-talk among structural domains of human DBP upon binding 25-hydroxyvitamin D

Biochem Biophys Res Commun. 2008 Jan 25;365(4):746-50. doi: 10.1016/j.bbrc.2007.11.033. Epub 2007 Nov 21.


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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Binding Sites
  • Humans
  • Protein Binding
  • Vitamin D / analogs & derivatives*
  • Vitamin D / chemistry
  • Vitamin D-Binding Protein / chemistry*


  • Vitamin D-Binding Protein
  • Vitamin D
  • 25-hydroxyvitamin D