Smith D F, Albers M W, Schreiber S L, Leach K L, Deibel M R
Department of Pharmacology, University of Nebraska Medical Center, Omaha 68198.
J Biol Chem. 1993 Nov 15;268(32):24270-3.
Avian progesterone receptor complexes contain five major co-purifying proteins, including hsp90, hsp70, and a 23-kDa protein. The other receptor-associated proteins, p50 and p54, share amino acid sequence similarities with a 52-59-kDa component (p59, hsp56, or FKBP52) of mammalian steroid receptor complexes that is also a member of the FK506-binding proteins (FKBP) family of immunophilins. We show here that p50, but not p54, cross-reacts with a rabbit antiserum prepared against human FKBP52. Both p50 and p54 bind an FK506 affinity resin at 0.5 M KCl, but only p50 binds efficiently in low salt conditions. Glycerol density gradient analyses show that both p50 and p54 exist predominantly in oligomeric complexes at low ionic strength. The poor retention of p54 on FK506 resin at low ionic strength compared with the high retention of p50 suggests that these proteins may largely exist in separate complexes and may interact with other proteins, such as progesterone receptor, in distinctive manners. In HeLa cell extracts, a 55-kDa FK506-binding protein, distinct from FKBP52, cross-reacts with anti-p54 antibody FF1. We conclude that p50 is avian FKBP52, whereas p54 and the 55-kDa human FF1 antigen are FKBP54, a novel immunophilin.
禽类孕酮受体复合物包含五种主要的共纯化蛋白，包括热休克蛋白90（hsp90）、热休克蛋白70（hsp70）和一种23 kDa的蛋白。其他与受体相关的蛋白，p50和p54，与哺乳动物类固醇受体复合物的一种52 - 59 kDa成分（p59、hsp56或FKBP52）具有氨基酸序列相似性，该成分也是亲免素FK506结合蛋白（FKBP）家族的成员。我们在此表明，p50而非p54与针对人FKBP52制备的兔抗血清发生交叉反应。p50和p54在0.5 M KCl条件下均能结合FK506亲和树脂，但只有p50在低盐条件下能有效结合。甘油密度梯度分析表明，在低离子强度下，p50和p54主要以寡聚复合物形式存在。与p50在低离子强度下在FK506树脂上的高保留率相比，p54的保留率较差，这表明这些蛋白可能主要以单独的复合物形式存在，并可能以独特的方式与其他蛋白（如孕酮受体）相互作用。在HeLa细胞提取物中，一种与FKBP52不同的55 kDa FK506结合蛋白与抗p54抗体FF1发生交叉反应。我们得出结论，p50是禽类FKBP52，而p54和55 kDa的人FF1抗原是FKBP54，一种新型亲免素。
