| 1. |
- Redecke, Lars, et al.
(author)
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Natively inhibited Trypanosoma brucei cathepsin B structure determined by using an X-ray laser.
- 2013
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In: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 339:6116, s. 227-30
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Journal article (peer-reviewed)abstract
- The Trypanosoma brucei cysteine protease cathepsin B (TbCatB), which is involved in host protein degradation, is a promising target to develop new treatments against sleeping sickness, a fatal disease caused by this protozoan parasite. The structure of the mature, active form of TbCatB has so far not provided sufficient information for the design of a safe and specific drug against T. brucei. By combining two recent innovations, in vivo crystallization and serial femtosecond crystallography, we obtained the room-temperature 2.1 angstrom resolution structure of the fully glycosylated precursor complex of TbCatB. The structure reveals the mechanism of native TbCatB inhibition and demonstrates that new biomolecular information can be obtained by the "diffraction-before-destruction" approach of x-ray free-electron lasers from hundreds of thousands of individual microcrystals.
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| 4. |
- Andersson, Fredrik, 1977, et al.
(author)
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Cyanobacterial ClpC/HSP100 protein displays intrinsic chaperone activity
- 2006
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In: Journal of Biological Chemistry. - 0021-9258. ; 281:9, s. 5468-5475
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Journal article (peer-reviewed)abstract
- HSP100 proteins are molecular chaperones that belong to the broader family of AAA+ proteins ( ATPases associated with a variety of cellular activities) known to promote protein unfolding, disassembly of protein complexes and translocation of proteins across membranes. The ClpC form of HSP100 is an essential, highly conserved, constitutively expressed protein in cyanobacteria and plant chloroplasts, and yet little is known regarding its specific activity as a molecular chaperone. To address this point, ClpC from the cyanobacterium Synechococcus elongatus (SyClpC) was purified using an Escherichia coli-based overexpression system. Recombinant SyClpC showed basal ATPase activity, similar to that of other types of HSP100 protein in non-photosynthetic organisms but different to ClpC in Bacillus subtilis. SyClpC also displayed distinct intrinsic chaperone activity in vitro, first by preventing aggregation of unfolded polypeptides and second by resolubilizing and refolding aggregated proteins into their native structures. The refolding activity of SyClpC was enhanced 3-fold in the presence of the B. subtilis ClpC adaptor protein MecA. Overall, the distinctive ClpC protein in photosynthetic organisms indeed functions as an independent molecular chaperone, and it is so far unique among HSP100 proteins in having both "holding" and disaggregase chaperone activities without the need of other chaperones or adaptor proteins.
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| 7. |
- Katikaridis, P, et al.
(author)
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ClpG Provides Increased Heat Resistance by Acting as Superior Disaggregase
- 2019
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In: Biomolecules. - : MDPI AG. - 2218-273X. ; 9:12
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Journal article (peer-reviewed)abstract
- Elevation of temperature within and above the physiological limit causes the unfolding and aggregation of cellular proteins, which can ultimately lead to cell death. Bacteria are therefore equipped with Hsp100 disaggregation machines that revert the aggregation process and reactivate proteins otherwise lost by aggregation. In Gram-negative bacteria, two disaggregation systems have been described: the widespread ClpB disaggregase, which requires cooperation with an Hsp70 chaperone, and the standalone ClpG disaggregase. ClpG co-exists with ClpB in selected bacteria and provides superior heat resistance. Here, we compared the activities of both disaggregases towards diverse model substrates aggregated in vitro and in vivo at different temperatures. We show that ClpG exhibits robust activity towards all disordered aggregates, whereas ClpB acts poorly on the protein aggregates formed at very high temperatures. Extreme temperatures are expected not only to cause extended protein unfolding, but also to result in an accelerated formation of protein aggregates with potentially altered chemical and physical parameters, including increased stability. We show that ClpG exerts higher threading forces as compared to ClpB, likely enabling ClpG to process “tight” aggregates formed during severe heat stress. This defines ClpG as a more powerful disaggregase and mechanistically explains how ClpG provides increased heat resistance.
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| 8. |
- Tryggvesson, Anders, 1975, et al.
(author)
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Characterization of ClpS2, an essential adaptor protein for the cyanobacterium Synechococcus elongatus
- 2015
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In: Febs Letters. - : Wiley. - 0014-5793. ; 589:24, s. 4039-4046
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Journal article (peer-reviewed)abstract
- The adaptor protein ClpS associates to the Clp protease and promotes degradation of N-end rule substrates in eubacteria and in algal/plant chloroplasts. Cyanobacteria are unusual in having two distinct ClpS paralogs. Although ClpS1 is typical of bacterial ClpS, ClpS2 differs in crucial ways. ClpS2 in Synechococcus elongatus is a relatively low- abundant, soluble protein essential for phototrophic growth. Like ClpS1, ClpS2 binds to the ClpCP3/R protease to block alpha-casein degradation and promote that of N-end rule substrates in vitro. However, their substrate specificity differs, with ClpS1 recognizing destabilizing Phe and Tyr residues at the substrate N-terminus whereas ClpS2 recognizes Leu. Overall, ClpS2 appears to have independently evolved in cyanobacteria to degrade a particular group of proteins, whose turnover is vital for cell viability. (C) 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
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| 9. |
- Tryggvesson, Anders, 1975, et al.
(author)
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Interaction specificity between the chaperone and proteolytic components of the cyanobacterial Clp protease
- 2012
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In: Biochemical Journal. - : Portland Press Ltd.. - 0264-6021 .- 1470-8728. ; 446, s. 311-320
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Journal article (peer-reviewed)abstract
- The Clp protease is conserved among eubacteria and most eukaryotes, and uses ATP to drive protein substrate unfolding and translocation into a chamber of sequestered proteolytic active sites. In plant chloroplasts and cyanobacteria, the essential constitutive Clp protease consists of the Hsp100/ClpC chaperone partnering a proteolytic core of catalytic ClpP and noncatalytic ClpR subunits. In the present study, we have examined putative determinants conferring the highly specific association between ClpC and the ClpP3/R core from the model cyanobacterium Synechococcus elongatus. Two conserved sequences in the N-terminus of ClpR (tyrosine and proline motifs) and one in the N-terminus of ClpP3 (MPIG motif) were identified as being crucial for the ClpC-ClpP3/R association. These N-terminal domains also influence the stability of the ClpP3/R core complex itself. A unique C-terminal sequence was also found in plant and cyanobacterial ClpC orthologues just downstream of the P-loop region previously shown in Escherichia coli to be important for Hsp100 association to ClpP. This R motif in Synechococcus ClpC confers specificity for the ClpP3/R core and prevents association with E. coli ClpP; its removal from ClpC reverses this core specificity.
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