Some characteristics of new tissue-binding proteins for metabolites of vitamin D other than 1,25-dihydroxyvitamin D |
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Authors: | D.E.M. Lawson Marilyn Charman P.W. Wilson S. Edelstein |
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Affiliation: | University of Cambridge and Medical Research Council, M.R.C. Dunn Nutrition Unit, Milton Road, Cambridge, CB4 1XJ U.K. |
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Abstract: | Protein(s) have been found in a wide range of tissues which have a high affinity for 25-hydroxycholecalciferol. Of the tissues examined only erythrocytes do not have this protein. The properties of the protein have been examined and it has been found that the association constants range from 2 · 109 to 5 · 109 M−1 and the sedimentation constants between 5.0 and 6.0 S. It was not possible to distinguish the proteins from the different tissues by their S values, mobility on gel electrophoresis or behaviour on ion-exchange chromatography. These techniques were all used, however, to show that the tissue 25-hydroxycholecalciferol binding protein is distinct from the main plasma binding protein for this steroid and from the intestinal 1,25-dihydroxycholecalciferol-binding protein. A protein has been found in the plasma of rachitic animals but not of normals, which is apparently indistinguishable from this new tissue 25-hydroxycholecalciferol-binding protein. The steroid specificity of this new binding protein has been shown to be dependent upon a C-25 hydroxyl group, and an intact conjugated double bond system. Possible functions for this protein have been briefly discussed. |
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Keywords: | cortisol 11β,17,21-trihydroxypregn-4-ene-3,20-dione cortexolone 17,21- dihydroxypregn-4-ene-3,20-dione dexamethasone 9α-fluoro-16α-methyl-11β,17,21-trihydroxy- pregna-1,4-diene-3,20-diene triamcinolone acetonide 11β,21-dihydroxy-9α-fluoropregna-1,4- diene-3,20-dione-16α,17α-acetonide |
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