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      Structural basis for the antifolding activity of a molecular chaperone

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          Abstract

          Molecular chaperones act on non-native proteins in the cell to prevent their aggregation, premature folding or misfolding. Different chaperones often exert distinct effects, such as acceleration or delay of folding, on client proteins via mechanisms that are poorly understood. Here we report the solution structure of SecB, a chaperone that exhibits strong antifolding activity, in complex with alkaline phosphatase (PhoA) and maltose binding protein (MBP) captured in their unfolded states. SecB uses long hydrophobic grooves that run around its disk-like shape to recognize and bind to multiple hydrophobic segments across the length of the non-native proteins. The multivalent binding mode results in proteins wrapping around SecB. This unique complex architecture alters the kinetics of protein binding to SecB and confers strong antifolding activity on the chaperone. The data show how the different architectures of chaperones result in distinct binding modes with non-native proteins that ultimately define the activity of the chaperone.

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          Most cited references38

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          Version 1.2 of the Crystallography and NMR system.

          Version 1.2 of the software system, termed Crystallography and NMR system (CNS), for crystallographic and NMR structure determination has been released. Since its first release, the goals of CNS have been (i) to create a flexible computational framework for exploration of new approaches to structure determination, (ii) to provide tools for structure solution of difficult or large structures, (iii) to develop models for analyzing structural and dynamical properties of macromolecules and (iv) to integrate all sources of information into all stages of the structure determination process. Version 1.2 includes an improved model for the treatment of disordered solvent for crystallographic refinement that employs a combined grid search and least-squares optimization of the bulk solvent model parameters. The method is more robust than previous implementations, especially at lower resolution, generally resulting in lower R values. Other advances include the ability to apply thermal factor sharpening to electron density maps. Consistent with the modular design of CNS, these additions and changes were implemented in the high-level computing language of CNS.
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            Automated NMR structure calculation with CYANA.

            This chapter gives an introduction to automated nuclear magnetic resonance (NMR) structure calculation with the program CYANA. Given a sufficiently complete list of assigned chemical shifts and one or several lists of cross-peak positions and columns from two-, three-, or four-dimensional nuclear Overhauser effect spectroscopy (NOESY) spectra, the assignment of the NOESY cross-peaks and the three-dimensional structure of the protein in solution can be calculated automatically with CYANA.
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              Is Open Access

              DnaK functions as a central hub in the E. coli chaperone network.

              Cellular chaperone networks prevent potentially toxic protein aggregation and ensure proteome integrity. Here, we used Escherichia coli as a model to understand the organization of these networks, focusing on the cooperation of the DnaK system with the upstream chaperone Trigger factor (TF) and the downstream GroEL. Quantitative proteomics revealed that DnaK interacts with at least ~700 mostly cytosolic proteins, including ~180 relatively aggregation-prone proteins that utilize DnaK extensively during and after initial folding. Upon deletion of TF, DnaK interacts increasingly with ribosomal and other small, basic proteins, while its association with large multidomain proteins is reduced. DnaK also functions prominently in stabilizing proteins for subsequent folding by GroEL. These proteins accumulate on DnaK upon GroEL depletion and are then degraded, thus defining DnaK as a central organizer of the chaperone network. Combined loss of DnaK and TF causes proteostasis collapse with disruption of GroEL function, defective ribosomal biogenesis, and extensive aggregation of large proteins. Copyright © 2012 The Authors. Published by Elsevier Inc. All rights reserved.
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                Author and article information

                Journal
                0410462
                6011
                Nature
                Nature
                Nature
                0028-0836
                1476-4687
                30 June 2016
                08 August 2016
                08 September 2016
                08 February 2017
                : 537
                : 7619
                : 202-206
                Affiliations
                Department of Biochemistry, Molecular Biology & Biophysics, University of Minnesota, Minneapolis, MN 55455
                Author notes
                Correspondence and requests for materials should be addressed to C.G.K. ( ckalodim@ 123456umn.edu )
                Article
                NIHMS798559
                10.1038/nature18965
                5161705
                27501151
                36391bdf-ce49-4b42-82c1-e90f742712d0

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