Structural highlights
Function
SSPB_HAEIN Enhances recognition of ssrA-tagged proteins by the ClpX-ClpP protease; the ssrA degradation tag (AANDENYALAA) is added trans-translationally to proteins that are stalled on the ribosome, freeing the ribosome and targeting stalled peptides for degradation. SspB activates the ATPase activity of ClpX. Seems to act in concert with SspA in the regulation of several proteins during exponential and stationary-phase growth (By similarity). Also stimulates degradation of the N-terminus of RseA (residues 1-108, alone or in complex with sigma-E) by ClpX-ClpP in a non-ssrA-mediated fashion (By similarity).
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
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.
Nucleotide-dependent substrate handoff from the SspB adaptor to the AAA+ ClpXP protease.,Bolon DN, Grant RA, Baker TA, Sauer RT Mol Cell. 2004 Nov 5;16(3):343-50. PMID:15525508[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Bolon DN, Grant RA, Baker TA, Sauer RT. Nucleotide-dependent substrate handoff from the SspB adaptor to the AAA+ ClpXP protease. Mol Cell. 2004 Nov 5;16(3):343-50. PMID:15525508 doi:10.1016/j.molcel.2004.10.001
