1ox8
Crystal structure of SspB
Structural highlights
FunctionSSPB_ECOLI 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.[1] [2] [3] 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.[4] [5] [6] 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 PubMedIn prokaryotes, incomplete or misfolded polypeptides emanating from a stalled ribosome are marked for degradation by the addition of an 11 residue peptide (AANDENYALAA) to their C terminus. Substrates containing this conserved degradation signal, the SsrA tag, are targeted to specific proteases including ClpXP and ClpAP. SspB was originally characterized as a stringent starvation protein and has been found to bind specifically to SsrA-tagged proteins and to enhance recognition of these proteins by the ClpXP degradation machine. Here, we report the crystal structures of SspB alone and in complex with an SsrA peptide. Unexpectedly, SspB exhibits a fold found in Sm-family RNA binding proteins. The dimeric SspB structures explain the key determinants for recognition of the SsrA tag and define a hydrophobic channel that may bind unfolded substrates. Structural basis of degradation signal recognition by SspB, a specificity-enhancing factor for the ClpXP proteolytic machine.,Song HK, Eck MJ Mol Cell. 2003 Jul;12(1):75-86. PMID:12887894[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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