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Structural modelling of the DNAJB6 oligomeric chaperone shows a peptide-binding cleft lined with conserved S/T-residues at the dimer interface.

ABSTRACT: The remarkably efficient suppression of amyloid fibril formation by the DNAJB6 chaperone is dependent on a set of conserved S/T-residues and an oligomeric structure, features unusual among DNAJ chaperones. We explored the structure of DNAJB6 using a combination of structural methods. Lysine-specific crosslinking mass spectrometry provided distance constraints to select a homology model of the DNAJB6 monomer, which was subsequently used in crosslink-assisted docking to generate a dimer model. A peptide-binding cleft lined with S/T-residues is formed at the monomer-monomer interface. Mixed isotope crosslinking showed that the oligomers are dynamic entities that exchange subunits. The purified protein is well folded, soluble and composed of oligomers with a varying number of subunits according to small-angle X-ray scattering (SAXS). Elongated particles (160 × 120 Å) were detected by electron microscopy and single particle reconstruction resulted in a density map of 20 Å resolution into which the DNAJB6 dimers fit. The structure of the oligomer and the S/T-rich region is of great importance for the understanding of the function of DNAJB6 and how it can bind aggregation-prone peptides and prevent amyloid diseases.

SUBMITTER: Soderberg CAG

PROVIDER: S-EPMC5979959 | biostudies-literature | 2018 Mar

REPOSITORIES: biostudies-literature

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Structural modelling of the DNAJB6 oligomeric chaperone shows a peptide-binding cleft lined with conserved S/T-residues at the dimer interface.

Söderberg Christopher A G CAG Månsson Cecilia C Bernfur Katja K Rutsdottir Gudrun G Härmark Johan J Rajan Sreekanth S Al-Karadaghi Salam S Rasmussen Morten M Höjrup Peter P Hebert Hans H Emanuelsson Cecilia C

Scientific reports 20180326 1

The remarkably efficient suppression of amyloid fibril formation by the DNAJB6 chaperone is dependent on a set of conserved S/T-residues and an oligomeric structure, features unusual among DNAJ chaperones. We explored the structure of DNAJB6 using a combination of structural methods. Lysine-specific crosslinking mass spectrometry provided distance constraints to select a homology model of the DNAJB6 monomer, which was subsequently used in crosslink-assisted docking to generate a dimer model. A p ...[more]

PMID: 29581438

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Project description:Small heat shock proteins (sHsps) are a family of ATP-independent molecular chaperones that function as "holdases" and prevent protein aggregation due to changes in temperature, pH, or oxidation state. sHsps have a conserved α-crystallin domain (ACD), which forms the dimer building block, flanked by variable N- and C-terminal regions. sHsps populate various oligomeric states as a function of their sequestrase activity, and these dynamic structural features allow the proteins to interact with a plethora of cellular substrates. However, the molecular mechanisms of their dynamic conformational assembly and the interactions with various substrates remains unclear. Therefore, it is important to gain insight into the underlying physicochemical properties that influence sHsp structure in an effort to understand their mechanism(s) of action. We evaluated several disease-relevant mutations, D109A, F113Y, R116C, R120G, and R120C, in the ACD of HspB5 for changes to in vitro chaperone activity relative to that of wildtype. Structural characteristics were also evaluated by ANS fluorescence and CD spectroscopy. Our results indicated that mutation Y113F is an efficient holdase, while D109A and R120G, which are found in patients with myofibrillar myopathy and cataracts, respectively, exhibit a large reduction in holdase activity in a chaperone-like light-scattering assay, which indicated alterations in substrate-sHsp interactions. The extent of the reductions in chaperone activities are different among the mutants and specific to the substrate protein, suggesting that while sHsps are able to interact with many substrates, specific interactions provide selectivity for some substrates compared to others. This work is consistent with a model for chaperone activity where key electrostatic interactions in the sHsp dimer provide structural stability and influence both higher-order sHsp interactions and facilitate interactions with substrate proteins that define chaperone holdase activity.

Dataset Information

Structural modelling of the DNAJB6 oligomeric chaperone shows a peptide-binding cleft lined with conserved S/T-residues at the dimer interface.

Publications

Structural modelling of the DNAJB6 oligomeric chaperone shows a peptide-binding cleft lined with conserved S/T-residues at the dimer interface.

Similar Datasets

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