title: Crystal structure of the heterodimeric complex of the adaptor, ClpS, with the N-domain of the AAA+ chaperone, ClpA.
abstract: Substrate selectivity and proteolytic activity for the E. coli ATP-dependent protease, ClpAP, is modulated by an adaptor protein, ClpS. ClpS binds to ClpA, the regulatory component of the ClpAP complex. We report the crystal structure of ClpS in complex with the isolated N-terminal domain of ClpA in two different crystal forms at 2.3- and 3.3-A resolution. The ClpS structure forms an alpha/beta-sandwich and is topologically analogous to the C-terminal domain of the ribosomal protein L7/L12. ClpS contacts two surfaces on the N-terminal domain in both crystal forms; the more extensive interface was shown to be favored in solution by protease protection experiments. The N-terminal 20 residues of ClpS are not visible in the crystal structures; the removal of the first 17 residues produces ClpSDeltaN, which binds to the ClpA N-domain but no longer inhibits ClpA activity. A zinc binding site involving two His and one Glu residue was identified crystallographically in the N-terminal domain of ClpA. In a model of ClpS bound to hexameric ClpA, ClpS is oriented with its N terminus directed toward the distal surface of ClpA, suggesting that the N-terminal region of ClpS may affect productive substrate interactions at the apical surface or substrate entry into the ClpA translocation channel.
authors.affiliation: Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: Fusheng
authors.initials: F
authors.lastname: Guo
authors.forename: Lothar
authors.initials: L
authors.lastname: Esser
authors.forename: Satyendra K
authors.initials: SK
authors.lastname: Singh
authors.forename: Michael R
authors.initials: MR
authors.lastname: Maurizi
authors.forename: Di
authors.initials: D
authors.lastname: Xia
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry*; D000595:Amino Acid Sequence; D001483:Base Sequence; D002352:Carrier Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D017931:DNA Primers; D019281:Dimerization; D049071:Endopeptidase Clp; D029968:Escherichia coli Proteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry*
chemical_list: D002352:Carrier Proteins; C454820:ClpS protein, E coli; D017931:DNA Primers; D029968:Escherichia coli Proteins; D011994:Recombinant Proteins; D012697:Serine Endopeptidases; C483568:ClpA protease, E coli; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases