3lgi | pdb_00003lgi
Structure of the protease domain of DegS (DegS-deltaPDZ) at 1.65 A
Structural highlights
Function[DEGS_ECOLI] When heat shock or other environmental stresses disrupt protein folding in the periplasm, DegS senses the accumulation of unassembled outer membrane porins (OMPs) and then initiates RseA (anti sigma-E factor) degradation by cleaving it in its periplasmic domain, making it an attractive substrate for subsequent cleavage by RseP. This cascade that ultimately leads to the sigma-E-driven expression of a variety of factors dealing with folding stress in the periplasm and OMP assembly.[1] [2] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedDegS is a periplasmic Escherichia coli protease, which functions as a trimer to catalyze the initial rate-limiting step in a proteolytic cascade that ultimately activates transcription of stress response genes in the cytoplasm. Each DegS subunit consists of a protease domain and a PDZ domain. During protein folding stress, DegS is allosterically activated by peptides exposed in misfolded outer membrane porins, which bind to the PDZ domain and stabilize the active protease. It is not known whether allostery is conferred by the PDZ domains or is an intrinsic feature of the trimeric protease domain. Here, we demonstrate that free DegS(DeltaPDZ) equilibrates between active and inactive trimers with the latter species predominating. Substrate binding stabilizes active DegS(DeltaPDZ) in a positively cooperative fashion. Mutations can also stabilize active DegS(DeltaPDZ) and produce an enzyme that displays hyperbolic kinetics and degrades substrate with a maximal velocity within error of that for fully activated, intact DegS. Crystal structures of multiple DegS(DeltaPDZ) variants, in functional and non-functional conformations, support a two-state model in which allosteric switching is mediated by changes in specific elements of tertiary structure in the context of an invariant trimeric base. Overall, our results indicate that protein substrates must bind sufficiently tightly and specifically to the functional conformation of DegS(DeltaPDZ) to assist their own degradation. Thus, substrate binding alone may have regulated the activities of ancestral DegS trimers with subsequent fusion of the protease domain to a PDZ domain, resulting in ligand-mediated regulation. Allostery is an intrinsic property of the protease domain of DegS: implications for enzyme function and evolution.,Sohn J, Grant RA, Sauer RT J Biol Chem. 2010 Oct 29;285(44):34039-47. Epub 2010 Aug 24. PMID:20739286[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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