The IbpA and IbpB small heat-shock proteins are substrates of the AAA plus Lon protease
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Author(s)
Bissonnette, Sarah A.
Rivera Rivera, Izarys
Baker, Tania
Sauer, Robert T
Date Issued
February 2010
Journal
Molecular Microbiology
Publisher
Blackwell Scientific Publications
Citation
Bissonnette, Sarah A. et al. “The IbpA and IbpB small heat-shock proteins are substrates of the AAA+ Lon protease.” Molecular Microbiology 75 (2010): 1539-1549. Web. 30 Nov. 2011. © 2010 Blackwell Publishing Ltd
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Final published version
Abstract
Small heat-shock proteins (sHSPs) are a widely conserved family of molecular chaperones, all containing a conserved α-crystallin domain flanked by variable N- and C-terminal tails. We report that IbpA and IbpB, the sHSPs of Escherichia coli, are substrates for the AAA+ Lon protease. This ATP-fueled enzyme degraded purified IbpA substantially more slowly than purified IbpB, and we demonstrate that this disparity is a consequence of differences in maximal Lon degradation rates and not in substrate affinity. Interestingly, however, IbpB stimulated Lon degradation of IbpA both in vitro and in vivo. Furthermore, although the variable N- and C-terminal tails of the Ibps were dispensable for proteolytic recognition, these tails contain critical determinants that control the maximal rate of Lon degradation. Finally, we show that E. coli Lon degrades variants of human α-crystallin, indicating that Lon recognizes conserved determinants in the folded α-crystallin domain itself. These results suggest a novel mode for Lon substrate recognition and provide a highly suggestive link between the degradation and sHSP branches of the protein quality-control network.
MIT Department
Massachusetts Institute of Technology. Department of Biology
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DOI of Published Version
https://doi.org/10.1111/j.1365-2958.2010.07070.x
