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.
Ray
Arjun
A
Bioorganic Chemistry & Structural Biology, Department of Medicine, Boston University School of Medicine, 85 East Newton Street, Boston, MA 02118, USA.
Swamy
Narasimha
N
Ray
Rahul
R
D001665:Binding Sites; D006801:Humans; D011485:Protein Binding; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000737:chemistry; D014809:Vitamin D-Binding Protein / Q000737:chemistry*
D014809:Vitamin D-Binding Protein; D014807:Vitamin D; C104450:25-hydroxyvitamin D