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Proc Natl Acad Sci U S A. 2013 May 28;110(22):E2002-8. doi: 10.1073/pnas.1307066110. Epub 2013 May 14.

Distinct quaternary structures of the AAA+ Lon protease control substrate degradation.

Author information

1
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

Abstract

Lon is an ATPase associated with cellular activities (AAA+) protease that controls cell division in response to stress and also degrades misfolded and damaged proteins. Subunits of Lon are known to assemble into ring-shaped homohexamers that enclose an internal degradation chamber. Here, we demonstrate that hexamers of Escherichia coli Lon also interact to form a dodecamer at physiological protein concentrations. Electron microscopy of this dodecamer reveals a prolate structure with the protease chambers at the distal ends and a matrix of N domains forming an equatorial hexamer-hexamer interface, with portals of ∼45 Å providing access to the enzyme lumen. Compared with hexamers, Lon dodecamers are much less active in degrading large substrates but equally active in degrading small substrates. Our results support a unique gating mechanism that allows the repertoire of Lon substrates to be tuned by its assembly state.

KEYWORDS:

ATP-dependent protease; EM structure; IbpB; regulated proteolysis; substrate gating

PMID:
23674680
PMCID:
PMC3670373
DOI:
10.1073/pnas.1307066110
[Indexed for MEDLINE]
Free PMC Article
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