title: Some characteristics of new tissue-binding proteins for metabolites of vitamin D other than 1,25-dihydroxyvitamin D.
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 constatns range from 2 - 10(9) to 5 - 10(9) 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 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.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001842:Bone and Bones / Q000378:metabolism; D002645:Chickens; D003600:Cytosol / Q000378:metabolism; D004100:Dihydroxycholecalciferols / Q000378:metabolism*; D006887:Hydroxycholecalciferols / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D009132:Muscles / Q000378:metabolism; D009928:Organ Specificity; D011485:Protein Binding; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D012867:Skin / Q000378:metabolism; D014807:Vitamin D / Q000378:metabolism*
chemical_list: D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D011506:Proteins; D014807:Vitamin D