The common 90-kd protein component of non-transformed '8S' steroid receptors is a heat-shock protein.
Non-transformed steroid receptors have an approximately 8S sedimentation coefficient that corresponds to an oligomeric structure of 250-300 kd which includes a non-hormone binding 90-kd protein. A monoclonal antibody BF4 raised against the purified, molybdate-stabilized, 8S progesterone receptor (8S-PR) from chick oviduct, recognizes 8S forms of all steroid hormone receptors. BF4 was found specific for a 90-kd protein present in great abundance in all chicken tissues, including that present in 8S-forms of steroid receptors. Here, using immunological and biochemical techniques, we demonstrate that this ubiquitous BF4-positive 90-kd protein is in fact the chicken 90 kd heat-shock protein (hsp 90): it increased in heat-shocked chick embryo fibroblasts, and displayed identical migration in two-dimensional gel electrophoresis and the same V8 peptide map as the already described hsp 90. We discuss the possibility that the interaction between hsp 90 and steroid hormone-binding subunits may play a role in keeping the receptor in an inactive form.
M G
MG
Catelli
N
N
Binart
I
I
Jung-Testas
J M
JM
Renoir
E E
EE
Baulieu
J R
JR
Feramisco
W J
WJ
Welch
D000818:Animals; D000911:Antibodies, Monoclonal; D002645:Chickens; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000032:analysis; D005260:Female; D006360:Heat-Shock Proteins / Q000032:analysis*; D046911:Macromolecular Substances; D008970:Molecular Weight; D010057:Oviducts / Q000378:metabolism; D011980:Receptors, Progesterone / Q000032:analysis*
D000911:Antibodies, Monoclonal; D000939:Epitopes; D006360:Heat-Shock Proteins; D046911:Macromolecular Substances; D011980:Receptors, Progesterone