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Cooperativity in the binding of 1α,25‐dihydroxyvitamin D 3 to the chick intestinal receptor
Author(s) -
Wilhelm Francois,
Norman Anthony W.
Publication year - 1984
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(84)81320-4
Subject(s) - cooperativity , scatchard plot , cooperative binding , dissociation constant , receptor , chemistry , hill differential equation , binding site , dissociation (chemistry) , stereochemistry , biophysics , biology , biochemistry , physics , exact differential equation , quantum mechanics , first order partial differential equation , partial differential equation
The binding of 1,25‐dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ] to its chick intestinal receptor does not fit well to the linear regression line of Scatchard's model ( r = −0.79; dissociation constant, K d = 0.51 nM). In fact, a concave ‘hook’ curve describes the data better. By using the Hill analysis the linear fitting was improved ( r = 0.99), the K d was found to be 0.14 nM and the Hill coefficient ( n H ) 1.42, which indicates a positive cooperativity in the binding of 1,25(OH) 2 D 3 to its receptor. Further we found that K d and n H are strongly correlated ( p < 0.001). These data suggest the existence of two ligand binding sites located in subunits for the 1,25(OH) 2 D 3 receptor.