Download MendeleyStructural Basis of an N-Degron Adaptor with More Stringent Specificity.
Stein, B.J., Grant, R.A., Sauer, R.T., Baker, T.A.(2016) Structure 24: 232-242
- PubMed: 26805523
- DOI: https://doi.org/10.1016/j.str.2015.12.008
- Primary Citation of Related Structures:
4YJM, 4YJX, 4YKA - PubMed 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.
Organizational Affiliation:
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
