title: The DegP and DegQ periplasmic endoproteases of Escherichia coli: specificity for cleavage sites and substrate conformation.
abstract: DegP and DegQ are homologous endoproteases found in the periplasmic compartment of Escherichia coli. The studies presented here suggest that DegP and DegQ have very similar substrate specificities and cleave substrates which are transiently or globally denatured. Model substrates were cleaved at discrete Val/Xaa or Ile/Xaa sites, suggesting that aliphatic, beta-branched residues, which are typically buried in the hydrophobic core of most proteins, are important determinants of cleavage specificity. Indeed, the peptide bonds cleaved in the model substrates are generally inaccessible in the native three-dimensional structures. In addition, a chimeric fusion protein, which is a DegP substrate in vivo, is degraded in vitro only after reduction of its intramolecular disulfide bonds. Taken together, these findings suggest that DegP and DegQ may degrade transiently denatured proteins, unfolded proteins which accumulate in the periplasm following heat shock or other stress conditions, and/or newly secreted proteins prior to folding and disulfide bond formation. Cross-linking studies indicate that both DegP and DegQ form dodecamers in solution and thus are similar to many other intracellular proteases which form large oligomeric complexes.
authors.affiliation: Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA. HKOLMAR@Uni-MolGen.gwdg.de
authors.forename: H
authors.initials: H
authors.lastname: Kolmar
authors.forename: P R
authors.initials: PR
authors.lastname: Waller
authors.forename: R T
authors.initials: RT
authors.lastname: Sauer
mesh_terms: D000595:Amino Acid Sequence; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D004220:Disulfides / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D008969:Molecular Sequence Data; D033903:Periplasmic Proteins; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism*; D013379:Substrate Specificity; D014764:Viral Proteins / Q000378:metabolism; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D004220:Disulfides; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D033903:Periplasmic Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; C016649:phage repressor proteins; C061682:DegP protease; C098059:DegQ protein, E coli; D012697:Serine Endopeptidases