title: Versatile modes of peptide recognition by the ClpX N domain mediate alternative adaptor-binding specificities in different bacterial species.
abstract: 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 SspBalpha 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 SspBalpha that play no detectable role in ClpX-binding or substrate delivery.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Tahmeena
authors.initials: T
authors.lastname: Chowdhury
authors.forename: Peter
authors.initials: P
authors.lastname: Chien
authors.forename: Shamsah
authors.initials: S
authors.lastname: Ebrahim
authors.forename: Robert T
authors.initials: RT
authors.lastname: Sauer
authors.forename: Tania A
authors.initials: TA
authors.lastname: Baker
mesh_terms: D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016935:Caulobacter crescentus / Q000201:enzymology*; D017124:Conserved Sequence; D049071:Endopeptidase Clp / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism; D009154:Mutation; D010455:Peptides / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D013379:Substrate Specificity
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D018832:Molecular Chaperones; D010455:Peptides; C477700:sspB protein, E coli; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases; C088072:ClpX protein, E coli; D000074183:ATPases Associated with Diverse Cellular Activities