ClpX interactions with ClpP, SspB, protein substrate and nucleotide

ClpXP and related ATP-dependent proteases are implements of cytosolic protein destruction. They couple chemical energy, derived from ATP hydrolysis, to the selection, unfolding, and degradation of protein substrates with the appropriate degradation signals. The ClpX component of ClpXP is a hexameric enzyme that recognizes protein substrates and unfolds them in an ATP-dependent reaction. Following unfolding, ClpX translocates the unfolded substrate into the ClpP peptidase for degradation. The best characterized degradation signal is the ssrA-degradation tag, which contains a binding site for ClpX and an adjacent binding site for the SspB adaptor protein. I show that the close proximity of these binding elements causes SspB binding to mask signals needed for ssrA-tag recognition by ClpX. The SspB dimer overcomes this signal masking by tethering itself and bound substrate to ClpX, via docking sites located in the dimeric N-terminal domain of ClpX. Because this N-domain dimer binds only a single SspB subunit, the ClpX hexamer can accommodate just one SspB dimer per hexamer. Other adaptor proteins that use these same tethering sites must compete with SspB for access to ClpXP. Substrates bearing ssrA tags with increased spacing between the SspB and ClpX binding elements are degraded more efficiently at low concentrations by ClpXP.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Biology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2006

Author dc:creator

• Hersch, Greg Louis

Advisor dc:contributor.advisor

• Robert T. Sauer.

• 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/1721.1/34199
• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Identifier URI

http://dspace.mit.edu/handle/1721.1/34199

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/34199