title: Versatile modes of peptide recognition by the AAA+ adaptor protein SspB.
abstract: Energy-dependent proteases often rely on adaptor proteins to modulate substrate recognition. The SspB adaptor binds peptide sequences in the stress-response regulator RseA and in ssrA-tagged proteins and delivers these molecules to the AAA+ ClpXP protease for degradation. The structure of SspB bound to an ssrA peptide is known. Here, we report the crystal structure of a complex between SspB and its recognition peptide in RseA. Notably, the RseA sequence is positioned in the peptide-binding groove of SspB in a direction opposite to the ssrA peptide, the two peptides share only one common interaction with the adaptor, and the RseA interaction site is substantially larger than the overlapping ssrA site. This marked diversity in SspB recognition of different target proteins indicates that it is capable of highly flexible and dynamic substrate delivery.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, 68-523, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors.forename: Igor
authors.initials: I
authors.lastname: Levchenko
authors.forename: Robert A
authors.initials: RA
authors.lastname: Grant
authors.forename: Julia M
authors.initials: JM
authors.lastname: Flynn
authors.forename: Robert T
authors.initials: RT
authors.lastname: Sauer
authors.forename: Tania A
authors.initials: TA
authors.lastname: Baker
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D049071:Endopeptidase Clp / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments; D011487:Protein Conformation; D012329:RNA, Bacterial / Q000737:chemistry / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D010446:Peptide Fragments; D012329:RNA, Bacterial; C477700:sspB protein, E coli; C096222:tmRNA; C483573:ClpXP protease, E coli; D049071:Endopeptidase Clp