Molecular Chaperone Machines: Chaperone Activities of the ...
Mov-W.M.1,0,31.1
Molecular Chaperone Machines: Chaperone Activities of the Cyclophilin Cyp-40 and the Steroid Aporeceptor-Associated Protein p23
p23. After incubation at 37°C, the reaction was supplemented with Hsp70, Hdj-1, or both and the recovery of 1-Gal activity was monitored. Hsp90 was highly effective in this chaperone maintenance and refolding
assay (Fig. 2). In the presence of Hsp90, 1-Gal was maintained in a folding-competent state throughout a 2-hour period at Molecular chaperones are essential proteins that participate in the regulation of steroid 37°C; likewise, both Cyp-40 and p23 were receptors in eukaryotes. The steroid aporeceptor complex contains the molecular chap- effective in maintaining 1-Gal in a foldingerones Hsp9O and Hsp7O, p48, the cyclophilin Cyp-40, and the associated proteins p23 competent state (at a 25:1 or 100:1 ratio, and p60. In vitro folding assays showed that Cyp-40 and p23 functioned as molecular respectively), albeit at an intermediate effichaperones in a manner similar to that of Hsp9O or Hsp7Q. Although neither Cyp-40 nor ciency relative to that of Hsp90 at equivap23 could completely refold an unfolded substrate, both proteins interacted with the lent concentrations (Fig. 2) (6). This mainsubstrate to maintain a nonnative folding-competent intermediate. Thus, the steroid tenance by Cyp-40 and p23 of the intermeaporeceptor complexes have multiple chaperone components that maintain substrates diate folded state was not dependent on in an intermediate folded state. nucleotide. Moreover, the ability of Cyp-40 to interact productively with the denatured substrate was not affected by the immunosuppressant drug cyclosporin A, which sugAlthough the general biochemical proper- refolding of a denatured protein substrate gests that the Cyp-40 chaperone activity is ties of certain molecular chaperones are alone or in conjunction with Hsp7O and not dependent on peptidylprolyl cis-trans well established, much less is known about Hdj-1 (Fig. 1) (8). A step in the chaperone- isomerase activity (9). In contrast to the how different chaperones interact with dependent folding reaction in which Hsp9O chaperone activities of Cyp-40 and p23, nonnative proteins in transient or stable exhibits a preferential ability to interact p60 (at concentrations up to -1000:1 mocomplexes (1). Within the eukaryotic cy- with a denatured protein substrate to main- lar excess) did not interact productively tosol, heteromeric complexes containing tain a nonnative folding-competent inter- with denatured 1-Gal (Fig. 2). Thus, p60 chaperones and other accessory proteins mediate has been characterized (6). This and Hdj-1 did not exhibit any activity as a have been identified, although their func- intermediate state corresponds to a function remains uncharacterized. Perhaps the tional nonnative protein that can undergo 30 A best studied of these complexes are steroid additional folding events (promoted by -0 Cyp-40 AO BSA -U- Hsp9O ] Hdj-1 aporeceptors that contain the heat shock Hsp7O and Hdj-1) that lead to the appear20 -+- Hsp7O 0- p23 proteins Hsp9O and Hsp7O, a Dnaj protein ance of the enzymatically active native proA p60 (Hdj-1), p60 (Stil), p48 (HiP), p23, and tein. Guanidine hydrochloride-denatured 10 the immunophilins (FKBP54, FKBP52, or 13-galactosidase (1-Gal) did not spontane-L.-Cyp-40) (2). The association of the chap- ously refold, even in the presence of Hsp90, n 10- -12 2 V -i.-- 50 c 50 100 150 200 250 erones Hsp90 and Hsp70 with glucocorti- Hsp7O, Cyp-40, p23, p60, or Hdj-1 (
Molecular Chaperone Machines: Chaperone Activities of the Cyclophilin Cyp-40 and the Steroid Aporeceptor-Associated Protein p23
p23. After incubation at 37°C, the reaction was supplemented with Hsp70, Hdj-1, or both and the recovery of 1-Gal activity was monitored. Hsp90 was highly effective in this chaperone maintenance and refolding
assay (Fig. 2). In the presence of Hsp90, 1-Gal was maintained in a folding-competent state throughout a 2-hour period at Molecular chaperones are essential proteins that participate in the regulation of steroid 37°C; likewise, both Cyp-40 and p23 were receptors in eukaryotes. The steroid aporeceptor complex contains the molecular chap- effective in maintaining 1-Gal in a foldingerones Hsp9O and Hsp7O, p48, the cyclophilin Cyp-40, and the associated proteins p23 competent state (at a 25:1 or 100:1 ratio, and p60. In vitro folding assays showed that Cyp-40 and p23 functioned as molecular respectively), albeit at an intermediate effichaperones in a manner similar to that of Hsp9O or Hsp7Q. Although neither Cyp-40 nor ciency relative to that of Hsp90 at equivap23 could completely refold an unfolded substrate, both proteins interacted with the lent concentrations (Fig. 2) (6). This mainsubstrate to maintain a nonnative folding-competent intermediate. Thus, the steroid tenance by Cyp-40 and p23 of the intermeaporeceptor complexes have multiple chaperone components that maintain substrates diate folded state was not dependent on in an intermediate folded state. nucleotide. Moreover, the ability of Cyp-40 to interact productively with the denatured substrate was not affected by the immunosuppressant drug cyclosporin A, which sugAlthough the general biochemical proper- refolding of a denatured protein substrate gests that the Cyp-40 chaperone activity is ties of certain molecular chaperones are alone or in conjunction with Hsp7O and not dependent on peptidylprolyl cis-trans well established, much less is known about Hdj-1 (Fig. 1) (8). A step in the chaperone- isomerase activity (9). In contrast to the how different chaperones interact with dependent folding reaction in which Hsp9O chaperone activities of Cyp-40 and p23, nonnative proteins in transient or stable exhibits a preferential ability to interact p60 (at concentrations up to -1000:1 mocomplexes (1). Within the eukaryotic cy- with a denatured protein substrate to main- lar excess) did not interact productively tosol, heteromeric complexes containing tain a nonnative folding-competent inter- with denatured 1-Gal (Fig. 2). Thus, p60 chaperones and other accessory proteins mediate has been characterized (6). This and Hdj-1 did not exhibit any activity as a have been identified, although their func- intermediate state corresponds to a function remains uncharacterized. Perhaps the tional nonnative protein that can undergo 30 A best studied of these complexes are steroid additional folding events (promoted by -0 Cyp-40 AO BSA -U- Hsp9O ] Hdj-1 aporeceptors that contain the heat shock Hsp7O and Hdj-1) that lead to the appear20 -+- Hsp7O 0- p23 proteins Hsp9O and Hsp7O, a Dnaj protein ance of the enzymatically active native proA p60 (Hdj-1), p60 (Stil), p48 (HiP), p23, and tein. Guanidine hydrochloride-denatured 10 the immunophilins (FKBP54, FKBP52, or 13-galactosidase (1-Gal) did not spontane-L.-Cyp-40) (2). The association of the chap- ously refold, even in the presence of Hsp90, n 10- -12 2 V -i.-- 50 c 50 100 150 200 250 erones Hsp90 and Hsp70 with glucocorti- Hsp7O, Cyp-40, p23, p60, or Hdj-1 (
