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Versatile modes of peptide recognition by the ClpX N domain mediate alternative adaptor‐binding specificities in different bacterial species
Author(s) -
Chowdhury Tahmeena,
Chien Peter,
Ebrahim Shamsah,
Sauer Robert T.,
Baker Tania A.
Publication year - 2010
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.306
Subject(s) - signal transducing adaptor protein , peptide , computational biology , domain (mathematical analysis) , plasma protein binding , chemistry , biology , microbiology and biotechnology , biophysics , biochemistry , signal transduction , mathematics , mathematical analysis
ClpXP, an AAA+ protease, plays key roles in protein‐quality control and many regulatory processes in bacteria. The N‐terminal domain of the ClpX component of ClpXP is involved in recognition of many protein substrates, either directly or by binding the SspB adaptor protein, which delivers specific classes of substrates for degradation. Despite very limited sequence homology between the E. coli and C. crescentus SspB orthologs, each of these adaptors can deliver substrates to the ClpXP enzyme from the other bacterial species. We show that the ClpX N domain recognizes different sequence determinants in the ClpX‐binding (XB) peptides of C. crescentus SspBα and E. coli SspB. The C. crescentus XB determinants span 10 residues and involve interactions with multiple side chains, whereas the E. coli XB determinants span half as many residues with only a few important side chain contacts. These results demonstrate that the N domain of ClpX functions as a highly versatile platform for peptide recognition, allowing the emergence during evolution of alternative adaptor‐binding specificities. Our results also reveal highly conserved residues in the XB peptides of both E. coli SspB and C. crescentus SspBα that play no detectable role in ClpX‐binding or substrate delivery.