1TWB

SspB disulfide crosslinked to an ssrA degradation tag

Summary for 1TWB

• Entry DOI: 10.2210/pdb1twb/pdb
• Descriptor: Stringent starvation protein B homolog, ssrA peptide (3 entities in total)
• Functional Keywords: adaptor, protease, aaa+, specificity factor, hydrolase
• Biological source: Haemophilus influenzae
• Total number of polymer chains: 4
• Total formula weight: 26699.91

Authors

Bolon, D.N.,Grant, R.A.,Baker, T.A.,Sauer, R.T. (deposition date: 2004-06-30, release date: 2004-11-16, Last modification date: 2024-11-06)

Primary citation

Bolon, D.N.,Grant, R.A.,Baker, T.A.,Sauer, R.T.
Nucleotide-Dependent Substrate Handoff from the SspB Adaptor to the AAA+ ClpXP Protease.
Mol.Cell, 16:343-350, 2004

PubMed Abstract: The SspB adaptor enhances ClpXP degradation by binding the ssrA degradation tag of substrates and the AAA+ ClpX unfoldase. To probe the mechanism of substrate delivery, we engineered a disulfide bond between the ssrA tag and SspB and demonstrated otherwise normal interactions by solving the crystal structure. Although the covalent link prevents adaptor.substrate dissociation, ClpXP degraded GFP-ssrA that was disulfide bonded to the adaptor. Thus, crosslinked substrate must be handed directly from SspB to ClpX. The ssrA tag in the covalent adaptor complex interacted with ClpX.ATPgammaS but not ClpX.ADP, suggesting that handoff occurs in the ATP bound enzyme. By contrast, SspB alone bound ClpX in both nucleotide states. Similar handoff mechanisms will undoubtedly be used by many AAA+ adaptors and enzymes, allowing assembly of delivery complexes in either nucleotide state, engagement of the recognition tag in the ATP state, and application of an unfolding force to the attached protein following hydrolysis.

PubMed: 15525508
DOI: 10.1016/j.molcel.2004.10.001

Experimental method

X-RAY DIFFRACTION (1.9 Å)