5nms

Hsp21 dodecamer, structural model based on cryo-EM and homology modellingHsp21 dodecamer, structural model based on cryo-EM and homology modelling

5nms, resolution 10.00Å Show:Asymmetric Unit Biological Assembly Structural highlights 5nms is a 12 chain structure with sequence from Arabidopsis thaliana. This structure supersedes the now removed PDB entry 5mb8. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 10Å Experimental data: Check Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function HS25P_ARATH Publication Abstract from PubMed Small heat shock proteins (sHsps) prevent aggregation of thermosensitive client proteins in a first line of defense against cellular stress. The mechanisms by which they perform this function have been hard to define due to limited structural information; currently there is only one high-resolution structure of a plant sHsp published, of the cytosolic Hsp16.9. We took interest in Hsp21, a chloroplast-localized sHsp crucial for plant stress resistance, which has even longer N-terminals arms than Hsp16.9, with a functionally important and conserved methionine-rich motif. To provide a framework for investigating structure-function relationships of Hsp21 and understanding these sequence variations, we developed a structural model of Hsp21 based on homology modeling, cryo-EM, crosslinking mass spectrometry, NMR and small angle X-ray scattering. Our data suggest a dodecameric arrangement of two trimer-of-dimer discs stabilized by the C-terminal tails, possibly through tail-to-tail interactions between the discs, mediated through extended IXVXI-motifs. Our model further suggests that six N-terminal arms are located on the outside of the dodecamer, accessible for interaction with client proteins, and distinct from previous undefined or inwardly-facing arms. To test the importance of the IXVXI motif, we created the point mutant V181A, which as expected disrupts the Hsp21 dodecamer and decreases chaperone activity. Finally, our data emphasize that sHsp chaperone efficiency depends on oligomerization and that client interactions can occur both with and without oligomer dissociation. These results provide a generalizable workflow to explore sHsps, expand our understanding of sHsp structural motifs, and provide a testable Hsp21 structure model to inform future investigations. Structural Model of Dodecameric Heat-shock Protein Hsp21 - Flexible N-terminal Arms Interact with Client Proteins while C-terminal Tails Maintain the Dodecamer and Chaperone Activity.,Rutsdottir G, Harmark J, Weide Y, Hebert H, Rasmussen MI, Wernersson S, Respondek M, Akke M, Hojrup P, Koeck PJ, Soderberg CA, Emanuelsson C J Biol Chem. 2017 Mar 21. pii: jbc.M116.766816. doi: 10.1074/jbc.M116.766816. PMID:28325834 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Heat Shock Protein structures