Multiple forms of molybdate-stabilized glucocorticoid-receptor complexes from HeLa cell cytosol.

Abstract

The investigation on hydrodynamic parameters of molybdate-stabilized glucocorticoid-receptor complexes from HeLa cell cytosol permitted resolution of four distinct forms. The first one could be detected in concentrated cytosols at low salt concentrations, and had the following properties: sedimentation coefficient = 9 S; Rs = 9.3 nm; Mr = 357,800; f/fo = 1.83; axial ratio (prolate ellipsoid) = 16. When these cytosol extracts were diluted, a second form could be detected with sedimentation coefficient = 8.3 S; Rs = 9.05 nm; Mr = 320,700; f/fo = 1.84; axial ratio = 16. Under high salt conditions, glucocorticoid-receptor complexes in concentrated cytosol had the following properties: sedimentation coefficient = 6.4 S; Rs = 6.7 nm; Mr = 183,100; f/fo = 1.64; axial ratio = 12. When either these cytosol extracts were diluted, or glucocorticoid-receptor complexes were subjected to repeated analysis, a fourth form was detected with sedimentation coefficient = 3.76 S; Rs = 5.67; Mr = 91,000; f/fo = 1.75; axial ratio = 14. Besides salt concentration and dilution, the time elapsed between sample dilution and analysis appeared to affect the hydrodynamic properties of glucocorticoid-receptor complexes. On the basis of our findings, it has been concluded that the most likely structure of molybdate-stabilized glucocorticoid-receptor complexes of HeLa cell cytosol can be represented by association of monomers in homodimers, and homotetramers. A homotrimer form could not be deduced from our findings, and the 320,700 glucocorticoid-receptor complex we observed has been suggested to represent an unresolved mixture of trimers and tetramers.