Degradation of the E. coli small heat-shock proteins by the AAA+ protease lon : significance to protein quality-control

The refolding and elimination of damaged and aggregated proteins requires the concerted effort of several branches of the protein quality-control network. This network includes refolding chaperones, disaggregases, holdases and proteases. Many years of investigation have led to a partial understanding of how different branches of the protein quality-control network cooperate with each other to accomplish the critical task of refolding or eliminating damaged and aggregated proteins. Here we investigate cooperation between the Lon protease and the IbpA and lbpB small heat-shock protein (sHSP) holdases in the model organism, Escherichia coli. sHSPs are molecular chaperones that bind unfolded proteins and prevent their irreversible aggregation. sHSPs contain a central a-crystallin domain flanked by variable N- and C-terminal tails. These tails are responsible for the higher-order oligomerization, and therefore the chaperone functions, of sHSPs. The E. coli genome contains two sHSPs, ibpA and ibpB. We find that IbpA and lbpB are substrates of the Lon protease when in their free form, and also when they are bound to unfolded client proteins in vivo and in vitro. Interestingly, unlike other known substrates of AAA+ proteases, lbpA and lbpB seem to be recognized through a structural feature of their conserved a-crystallin domain, rather than through peptide motifs near their N- or C-termini.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Biology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2010

Author dc:creator

• Bissonnette, Sarah Ayano

Advisor dc:contributor.advisor

• Tania A. Baker.

• Biology.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/58167

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/58167