title: Quantitative assessment of complex formation of nuclear-receptor accessory proteins.
abstract: Like other nuclear receptors, steroid hormone receptors form large protein hetero-complexes in their inactive, ligand-friendly state. Several heat-shock proteins, immunophilins and others have been identified as members of these highly dynamic complexes. The interaction kinetics and dynamics of hsp90, hsp70, p60 (Hop), FKBP52, FKBP51, p48 (Hip) and p23 have been assessed by a biosensor approach measuring the complex formation in real time. A core chaperone complex has been reconstituted from p60, hsp90 and hsp70. p60 forms a molecular bridge between hsp90 and hsp70 with an affinity in the range of 10(5) M(-1). Dynamics of hsp90-p60 complex formation is modulated by ATP through changes in the co-operativity of interaction. At low protein concentrations ATP stabilizes the complex. Binding of p23 to hsp90 did not change the affinity of the hsp90-p60 complex and the stabilizing effect of ATP. Saturation of the p48-hsp70 interaction could not be achieved, suggesting multiple binding sites. A picture of the protein complex, including stoichiometric coefficients, co-operativity of interaction and equilibrium-binding constants, has been formed.
authors.affiliation: Institute for Applied Microbiology, University of the Agricultural Sciences, Muthgasse 18, A-1190 Vienna, Austria.
authors.forename: K
authors.initials: K
authors.lastname: Graumann
authors.forename: A
authors.initials: A
authors.lastname: Jungbauer
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D001671:Biochemistry / Q000379:methods; D015374:Biosensing Techniques; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D047628:Estrogen Receptor alpha; D005982:Glutathione Transferase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000302:isolation & purification / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000302:isolation & purification / Q000378:metabolism; D015151:Immunoblotting; D020104:Immunophilins / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D018832:Molecular Chaperones; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011489:Protein Denaturation; D011960:Receptors, Estrogen / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D020349:Surface Plasmon Resonance; D022021:Tacrolimus Binding Proteins; D025521:Tumor Suppressor Proteins
chemical_list: D002352:Carrier Proteins; D047628:Estrogen Receptor alpha; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009687:Nuclear Proteins; D011960:Receptors, Estrogen; D011994:Recombinant Proteins; C101119:ST13 protein, human; D025521:Tumor Suppressor Proteins; D000255:Adenosine Triphosphate; D005982:Glutathione Transferase; D022021:Tacrolimus Binding Proteins; D020104:Immunophilins