Abstract
Molecular chaperones influence the process of protein folding and, under conditions of stress, recognize non-native proteins to ensure that misfolded proteins neither appear nor accumulate. BAG-1, identified as an Hsp70 associated protein, was shown to have the unique properties of a negative regulator of Hsp70. Here, we demonstrate that BAG-1 inhibits the in vitro protein refolding activity of Hsp70 by forming stable ternary complexes with non-native substrates that do not release even in the presence of nucleotide and the co-chaperone, Hdj-1. However, the substrate in the BAG-1-containing ternary complex does not aggregate and remains in a soluble intermediate folded state, indistinguishable from the refolding-competent substrate-Hsp70 complex. BAG-1 neither inhibits the Hsp70 ATPase, nor has the properties of a nucleotide exchange factor; instead, it stimulates ATPase activity, similar to that observed for Hdj-1, but with opposite consequences. In the presence of BAG-1, the conformation of Hsp70 is altered such that the substrate binding domain becomes less accessible to protease digestion, even in the presence of nucleotide and Hdj-1. These results suggest a mechanistic basis for BAG-1 as a negative regulator of the Hsp70-Hdj-1 chaperone cycle.
| Original language | English |
|---|---|
| Pages (from-to) | 6871-6878 |
| Number of pages | 8 |
| Journal | EMBO Journal |
| Volume | 17 |
| Issue number | 23 |
| DOIs | |
| Publication status | Published - 1998 Dec 1 |
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All Science Journal Classification (ASJC) codes
- Neuroscience(all)
- Molecular Biology
- Biochemistry, Genetics and Molecular Biology(all)
- Immunology and Microbiology(all)
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BAG-1, a negative regulator of Hsp70 chaperone activity, uncouples nucleotide hydrolysis from substrate release. / Bimston, David; Song, Jaewhan; Winchester, David; Takayama, Shinichi; Reed, John C.; Morimoto, Richard I.
In: EMBO Journal, Vol. 17, No. 23, 01.12.1998, p. 6871-6878.Research output: Contribution to journal › Article
TY - JOUR
T1 - BAG-1, a negative regulator of Hsp70 chaperone activity, uncouples nucleotide hydrolysis from substrate release
AU - Bimston, David
AU - Song, Jaewhan
AU - Winchester, David
AU - Takayama, Shinichi
AU - Reed, John C.
AU - Morimoto, Richard I.
PY - 1998/12/1
Y1 - 1998/12/1
N2 - Molecular chaperones influence the process of protein folding and, under conditions of stress, recognize non-native proteins to ensure that misfolded proteins neither appear nor accumulate. BAG-1, identified as an Hsp70 associated protein, was shown to have the unique properties of a negative regulator of Hsp70. Here, we demonstrate that BAG-1 inhibits the in vitro protein refolding activity of Hsp70 by forming stable ternary complexes with non-native substrates that do not release even in the presence of nucleotide and the co-chaperone, Hdj-1. However, the substrate in the BAG-1-containing ternary complex does not aggregate and remains in a soluble intermediate folded state, indistinguishable from the refolding-competent substrate-Hsp70 complex. BAG-1 neither inhibits the Hsp70 ATPase, nor has the properties of a nucleotide exchange factor; instead, it stimulates ATPase activity, similar to that observed for Hdj-1, but with opposite consequences. In the presence of BAG-1, the conformation of Hsp70 is altered such that the substrate binding domain becomes less accessible to protease digestion, even in the presence of nucleotide and Hdj-1. These results suggest a mechanistic basis for BAG-1 as a negative regulator of the Hsp70-Hdj-1 chaperone cycle.
AB - Molecular chaperones influence the process of protein folding and, under conditions of stress, recognize non-native proteins to ensure that misfolded proteins neither appear nor accumulate. BAG-1, identified as an Hsp70 associated protein, was shown to have the unique properties of a negative regulator of Hsp70. Here, we demonstrate that BAG-1 inhibits the in vitro protein refolding activity of Hsp70 by forming stable ternary complexes with non-native substrates that do not release even in the presence of nucleotide and the co-chaperone, Hdj-1. However, the substrate in the BAG-1-containing ternary complex does not aggregate and remains in a soluble intermediate folded state, indistinguishable from the refolding-competent substrate-Hsp70 complex. BAG-1 neither inhibits the Hsp70 ATPase, nor has the properties of a nucleotide exchange factor; instead, it stimulates ATPase activity, similar to that observed for Hdj-1, but with opposite consequences. In the presence of BAG-1, the conformation of Hsp70 is altered such that the substrate binding domain becomes less accessible to protease digestion, even in the presence of nucleotide and Hdj-1. These results suggest a mechanistic basis for BAG-1 as a negative regulator of the Hsp70-Hdj-1 chaperone cycle.
UR - http://www.scopus.com/inward/record.url?scp=0032402812&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032402812&partnerID=8YFLogxK
U2 - 10.1093/emboj/17.23.6871
DO - 10.1093/emboj/17.23.6871
M3 - Article
C2 - 9843493
AN - SCOPUS:0032402812
VL - 17
SP - 6871
EP - 6878
JO - EMBO Journal
JF - EMBO Journal
SN - 0261-4189
IS - 23
ER -