Subunit arrangement in the dodecameric chloroplast small heat shock protein Hsp21

Lambert, Wietske; Koeck, Philip J.B.; Åhrman, Emma; Purhonen, Pasi; Cheng, Kimberley; Elmlund, Dominika; Hebert, Hans; Emanuelsson, Cecilia

doi:10.1002/pro.560

Cited by 31 publications

(40 citation statements)

References 41 publications

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“…Numerous substrate-binding sites and intra-oligomer interaction sites were mapped on to its N-terminal arm (Ahrman et al 2007). A structure model of Hsp21, from single-particle electron microscopy studies showed that it too existed as a doubledisc dodecamer, albeit with a relative rotation between the two discs, when compared with the wheat Hsp16.9 dodecamer (Lambert et al 2011). Our studies of the tagged and tagless constructs of rice Hsp26.7 confirm that the length of the Nterminal region has a direct bearing on its oligomer assembly and chaperone activity.…”

Section: Hsp267 Chloroplastmentioning

confidence: 56%

Characterization of rice small heat shock proteins targeted to different cellular organelles

Mani

Ramakrishna

Suguna

2015

Cell Stress and Chaperones

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Small heat shock proteins (sHSPs) are a family of ATP-independent molecular chaperones which prevent cellular protein aggregation by binding to misfolded proteins. sHSPs form large oligomers that undergo drastic rearrangement/dissociation in order to execute their chaperone activity in protecting substrates from stress. Substrate-binding sites on sHSPs have been predominantly mapped on their intrinsically disordered N-terminal arms. This region is highly variable in sequence and length across species, and has been implicated in both oligomer formation and in mediating chaperone activity. Here, we present our results on the functional and structural characterization of five sHSPs in rice, each differing in their subcellular localisation, viz., cytoplasm, nucleus, chloroplast, mitochondria and peroxisome. We performed activity assays and dynamic light scattering studies to highlight differences in the chaperone activity and quaternary assembly of sHSPs targeted to various organelles. By cloning constructs that differ in the length and sequence of the tag in the N-terminal region, we have probed the sensitivity of sHSP oligomer assembly and chaperone activity to the length and amino acid composition of the N-terminus. In particular, we have shown that the incorporation of an N-terminal tag has significant consequences on sHSP quaternary structure.

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Section: Hsp267 Chloroplastmentioning

confidence: 56%

Characterization of rice small heat shock proteins targeted to different cellular organelles

Mani

Ramakrishna

Suguna

2015

Cell Stress and Chaperones

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“…The chloroplast-localized sHsp, Hsp21, increases plant resistance to heat stress upon overexpression (Harndahl et al 1999), and we have previously characterized its structure and function (Ahrman et al 2007a, b;Lambert et al 2011a). We found that Hsp21 has an even better chaperone activity compared with human αB-crystallin, the most wellcharacterized sHsp.…”

Section: Introductionmentioning

confidence: 71%

Probing the transient interaction between the small heat-shock protein Hsp21 and a model substrate protein using crosslinking mass spectrometry

Lambert

Rutsdottir

Hussein

et al. 2013

Cell Stress and Chaperones

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Small heat-shock protein chaperones are important players in the protein quality control system of the cell, because they can immediately respond to partially unfolded proteins, thereby protecting the cell from harmful aggregates. The small heat-shock proteins can form large polydisperse oligomers that are exceptionally dynamic, which is implicated in their function of protecting substrate proteins from aggregation. Yet the mechanism of substrate recognition remains poorly understood, and little is known about what parts of the small heat-shock proteins interact with substrates and what parts of a partially unfolded substrate protein interact with the small heat-shock proteins. The transient nature of the interactions that prevent substrate aggregation rationalize probing this interaction by crosslinking mass spectrometry. Here, we used a workflow with lysine-specific crosslinking and offline nano-liquid chromatography matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry to explore the interaction between the plant small heat-shock protein Hsp21 and a thermosensitive model substrate protein, malate dehydrogenase. The identified crosslinks point at an interaction between the disordered N-terminal region of Hsp21 and the C-terminal presumably unfolding part of the substrate protein.

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“…This micro-heterogeneity adds an additional level to the quaternary complexity of the sHSPs exchange of HSP26 could only be quantitatively understood by invoking at least two separate dissociation rate constants, consistent with two types of oligomers [83]. Differences were noted between negative-stain EM reconstructions of Arabidopsis thaliana HSP21, in the presence or absence of cross-linker, hinting at the possibility of multiple conformations differing in terms of compactness [96]. A similar observation was also made in a negative-stain EM study of the octahedral HSP16.5 and Archaeoglobus fulgidus HSP20.2 24mers.…”

Section: Shsp Oligomers Can Transition Between Compact and Expanded Fmentioning

confidence: 89%

Small Heat-Shock Proteins: Paramedics of the Cell

Hilton

Lioe

Stengel

et al. 2012

Topics in Current Chemistry

124

129

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The small heat-shock proteins (sHSPs) comprise a family of molecular chaperones which are widespread but poorly understood. Despite considerable effort, comparatively few high-resolution structures have been determined for the sHSPs, a likely consequence of their tendency to populate ensembles of inter-converting conformational and oligomeric states at equilibrium. This dynamic structure appears to underpin the sHSPs' ability to bind and sequester target proteins rapidly, and renders them the first line of defence against protein aggregation during disease and cellular stress. Here we describe recent studies on the sHSPs, with a particular focus on those which have provided insight into the structure and dynamics of these proteins. The combined literature reveals a picture of a remarkable family of molecular chaperones whose thermodynamic and kinetic properties are exquisitely balanced to allow functional regulation by subtle changes in cellular conditions.

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Subunit arrangement in the dodecameric chloroplast small heat shock protein Hsp21

Cited by 31 publications

References 41 publications

Characterization of rice small heat shock proteins targeted to different cellular organelles

Characterization of rice small heat shock proteins targeted to different cellular organelles

Probing the transient interaction between the small heat-shock protein Hsp21 and a model substrate protein using crosslinking mass spectrometry

Small Heat-Shock Proteins: Paramedics of the Cell

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