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Structure. 2016 Feb 2;24(2):232-42. doi: 10.1016/j.str.2015.12.008. Epub 2016 Jan 21.

Structural Basis of an N-Degron Adaptor with More Stringent Specificity.

Author information

1
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
2
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Electronic address: tabaker@mit.edu.

Abstract

The N-end rule dictates that a protein's N-terminal residue determines its half-life. In bacteria, the ClpS adaptor mediates N-end-rule degradation, by recognizing proteins bearing specific N-terminal residues and delivering them to the ClpAP AAA+ protease. Unlike most bacterial clades, many α-proteobacteria encode two ClpS paralogs, ClpS1 and ClpS2. Here, we demonstrate that both ClpS1 and ClpS2 from A. tumefaciens deliver N-end-rule substrates to ClpA, but ClpS2 has more stringent binding specificity, recognizing only a subset of the canonical bacterial N-end-rule residues. The basis of this enhanced specificity is addressed by crystal structures of ClpS2, with and without ligand, and structure-guided mutagenesis, revealing protein conformational changes and remodeling in the substrate-binding pocket. We find that ClpS1 and ClpS2 are differentially expressed during growth in A. tumefaciens and conclude that the use of multiple ClpS paralogs allows fine-tuning of N-end-rule degradation at the level of substrate recognition.

PMID:
26805523
PMCID:
PMC4979544
DOI:
10.1016/j.str.2015.12.008
[Indexed for MEDLINE]
Free PMC Article

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