Physico-chemical properties of the hydroxysterol binding protein of human lymphocyte cytosol. Effects of high salt concentrations and molybdate.
Side chain-hydroxylated derivatives of cholesterol (OH sterol) inhibiting lymphoblastic transformation bind with high affinity and specificity to a hydroxysterol binding protein (OHSBP) in the cytosol of human lymphocytes. These binding properties of OHSBP suggested some analogies with that of steroid hormone receptors. The observation of a nuclear binding of 25-OH[3H]cholesterol prompted us to apply to the cytosolic OH sterol-OHSBP complex the physico-chemical treatments known to 'activate' the steroid hormone receptors. A change of sedimentation coefficient from 8.3 to 4.3 S was observed in hypertonic buffer (0.4 M KCl) but the resulting 4.3 S complex dissociates easily whereas the 'native' 8.3 S form does not. Moreover, molybdate did not prevent the 8.3----4.3 S transformation induced by KCl and neither ammonium sulfate precipitation nor increasing temperature had any effect on the sedimentation coefficient of the 8.3 S complex. Thus, several physico-chemical features differentiate the OH sterol-OHSBP complex from steroid hormone receptors.
D001667:Binding, Competitive; D002352:Carrier Proteins / Q000097:blood* / Q000302:isolation & purification; D002467:Cell Nucleus / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D006888:Hydroxycholesterols / Q000097:blood; D007700:Kinetics; D008214:Lymphocytes / Q000378:metabolism*; D008982:Molybdenum / Q000494:pharmacology*; D009994:Osmolar Concentration; D014316:Tritium; D009124:Muscle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins
D002352:Carrier Proteins; D006888:Hydroxycholesterols; D008982:Molybdenum; D014316:Tritium; C007997:25-hydroxycholesterol; C024687:sodium molybdate(VI); C101149:FHL1 protein, human; D009124:Muscle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins