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- Babu Moparthi, Satish, et al.
(författare)
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Transient conformational remodeling of folding proteins by GroES - Individually and in concert with GroEL
- 2014
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Ingår i: Journal of chemical biology. - : Springer Berlin/Heidelberg. - 1864-6158 .- 1864-6166. ; 7:1, s. 1-15
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Forskningsöversikt (refereegranskat)abstract
- The commonly accepted dogma of the bacterial GroE chaperonin system entails protein folding mediated by cycles of several ATP-dependent sequential steps where GroEL interacts with the folding client protein. In contrast, we herein report GroES-mediated dynamic remodeling (expansion and compression) of two different protein substrates during folding: the endogenous substrate MreB and carbonic anhydrase (HCAII), a well-characterized protein folding model. GroES was also found to influence GroEL binding induced unfolding and compression of the client protein underlining the synergistic activity of both chaperonins, even in the absence of ATP. This previously unidentified activity by GroES should have important implications for understanding the chaperonin mechanism and cellular stress response. Our findings necessitate a revision of the GroEL/ES mechanism.
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| 2. |
- Villebeck, Laila, et al.
(författare)
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Conformational Rearrangements of Tail-less Complex Polypeptide 1 (TCP-1) Ring Complex (TRiC)-Bound Actin
- 2007
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 46:17, s. 5083-5093
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism of chaperonins is still under intense investigation. Earlier studies by others and us on the bacterial chaperonin GroEL points to an active role of chaperonins in unfolding the target protein during initial binding. Here, a natural eukaryotic chaperonin system [tail-less complex polypeptide 1 (TCP-1) ring complex (TRiC) and its target protein actin] was investigated to determine if the active participation of the chaperonin in the folding process is evolutionary-conserved. Using fluorescence resonance energy transfer (FRET) measurements on four distinct doubly fluorescein-labeled variants of actin, we have obtained a fairly detailed map of the structural rearrangements that occur during the TRiC−actin interaction. The results clearly show that TRiC has an active role in rearranging the bound actin molecule. The target is stretched as a consequence of binding to TRiC and further rearranged in a second step as a consequence of ATP binding; i.e., the mechanism of chaperonins is conserved during evolution.
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| 3. |
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| 4. |
- Villebeck, Laila, et al.
(författare)
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Domain-specific chaperone-induced expansion is required for ß-actin folding : a comparison of ß-actin conformations upon interactions with GroEL and tail-less complex polypeptide 1 ring complex (TRiC)
- 2007
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 46:44, s. 12639-12647
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Tidskriftsartikel (refereegranskat)abstract
- Actin, an abundant cytosolic protein in eukaryotic cells, is dependent on the interaction with the chaperonin tail-less complex polypeptide 1 ring complex (TRiC) to fold to the native state. The prokaryotic chaperonin GroEL also binds non-native ß-actin, but is unable to guide ß-actin toward the native state. In this study we identify conformational rearrangements in ß-actin, by observing similarities and differences in the action of the two chaperonins. A cooperative collapse of ß-actin from the denatured state to an aggregation-prone intermediate is observed, and insoluble aggregates are formed in the absence of chaperonin. In the presence of GroEL, however, >90% of the aggregation-prone actin intermediate is kept in solution, which shows that the binding of non-native actin to GroEL is effective. The action of GroEL on bound flourescein-labeled ß-actin was characterized, and the structural rearrangement was compared to the case of the ß-actin-TRiC complex, employing the homo fluorescence resonance energy transfer methodology previously used [Villebeck, L., Persson, M., Luan, S.-L., Hammarström, P., Lindgren, M., and Jonsson, B.-H. (2007) Biochemistry 46 (17), 5083-93]. The results suggest that the actin structure is rearranged by a "binding-induced expansion" mechanism in both TRiC and GroEL, but that binding to TRiC, in addition, causes a large and specific separation of two subdomains in the ß-actin molecule, leading to a distinct expansion of its ATP-binding cleft. Moreover, the binding of ATP and GroES has less effect on the GroEL-bound ß-actin molecule than the ATP binding to TRiC, where it leads to a major compaction of the ß-actin molecule. It can be concluded that the specific and directed rearrangement of the ß-actin structure, seen in the natural ß-actin-TRiC system, is vital for guiding ß-actin to the native state. © 2007 American Chemical Society.
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| 5. |
- Villebeck, Laila, et al.
(författare)
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Interactions Between the Bacterial β-actin Homologue MreB and the Group I Chaperonin GroEL and Group II Chaperonin TRiC
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This pilot study on the interaction between MreB andthe chaperonins TRiC and GroEL indicates that thefolding of the actin ancestor was facilitated by thechaperonins. From an evolutionary point of view, it isinteresting to investigate the nature of the bindinginteraction between the prokaryotic system MreB-GroELand compare it to the binding interaction between actinand TRiC and the following questions will be addressed:Does MreB refold in a spontaneous manner or is itsfolding dependent on the action of a chaperonin (GroEL)as in the case of actin folding (TRiC)? Does MreB bind ina similar stretched manner to GroEL as actin binds toTRiC (4, 11), or is the “general” binding inducedunfolding sufficient for guiding MreB to the native state?How does the MreB molecule interact with TRiC, is therea similar stretching as for actin? Are there any analoguessequences between actin and TRiC that are recognized byTRiC and/or GroEL? Two single variants where cysteines have beenintroduced at positions 69 and 245 in E. coli MreB(Figure 1 B). These positions are situated at the tips of thecorresponding subdomains 2 and 4 of the actin molecule(4, 12). The double variant N69C/V245C has also beenconstructed. The three variants will be produced andlabeled with fluorescein and subsequent homo-FRETmeasurements will be performed on MreB bound toGroEL, TRiC and GroES. The results will be comparedto the results on actin bound to the chaperonins toinvestigate how the chaperonin-dependent folding ofactin homologues has evolved.
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| 6. |
- Villebeck, Laila, et al.
(författare)
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Mapping the Different Interactions between Eukaryotic β-actin and the Group I (GroEL) and Group II (TRiC) Chaperonins
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Productive folding to the native state of the abundant eukaryotic protein actin is dependent on the chaperonin TRiC. The prokaryotic chaperonin GroEL also recognizes actin, but this interaction does not lead to the correct folding of actin. It is well established that GroEL interacts with non-native proteins through hydrophobic interactions. The characteristics of the interactions between TRiC and its target proteins are however unclear. In this study, we present multiple site-directed cysteine labeling and fluorescence measurements indicating that actin initially binds to TRiC through several interaction sites and that the surfaces of the interaction areas on the walls of the TRiC chamber present both polar and hydrophobic residues. At a later stage in the chaperonin cycle, the binding of ATP causes conformational changes in the chaperonin, which leads to a presentation of a more hydrophobic milieu in TRiC chamber. The conformational changes of the chaperonin causes rearrangements of the actin molecule and new interactions are proposed to be formed. Additionally, we show that the initial binding of actin to TRiC leads to a re-modeling of the nucleotide-binding cleft in actin. We also present data indicating that GroEL presents less specific interaction areas towards the bound actin than TRiC does. The interactions between actin and GroEL are tight and of hydrophobic character. No re-modeling of the nucleotide-binding cleft was obtained in the actin-GroEL complex. We conclude that the interactions between actin and TRiC are of both polar and hydrophobic character, the nature of the interactions are different in the prokaryotic and eukaryotic chaperonins, and the rearrangements of the nucleotide binding cleft of actin seen in the chaperonin cycle of TRiC do not occur in GroEL. We suggest that the rearrangements of the nucleotide-binding site in actin are critical for productive folding of actin.
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| 7. |
- Villebeck, Laila, 1976-
(författare)
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Structural rearrangements of actins interacting with the Chaperonin systems TRiC/Prefoldin and GroEL/ES
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The studies in this thesis are mainly focused on the effects that the chaperonin mechanisms have on a bound target protein. Earlier studies have shown that the bacterial chaperonin GroEL plays an active role in unfolding a target protein during the initial binding. Here, the effects of the eukaryotic chaperonin TRiC’s mechanical action on a bound target protein were studied by fluorescence resonance energy transfer (FRET) measurements by attaching the fluorophore fluorescein to specific positions in the structure of the target protein, β-actin. Actin is an abundant eukaryotic protein and is dependent on TRiC to reach its native state. It was found that at the initial binding to TRiC, the actin structure is stretched, particularly across the nucleotide-binding site. This finding led to the conclusion that the binding-induced unfolding mechanism is conserved through evolution. Further studies indicated that in a subsequent step of the chaperonin cycle, the actin molecule collapses. This collapse leads to rearrangements of the structure at the nucleotide-binding cleft, which is also narrowed as a consequence.As a comparison to the productive folding of actin in the TRiC chaperonin system, FRET studies were also performed on actin interacting with GroEL. This is a non-productive interaction in terms of guiding actin to its native state. The study presents data indicating that the nucleotide-binding cleft in actin is not rearranged by GroEL in the same way as it is rearranged during the TRiC interaction. Thus, it could be concluded that although the general unfolding mechanism is conserved through the evolution of the chaperonins, an additional and specific binding to distinct parts of the actin molecule has evolved in TRiC. This specific binding leads to a directed unfolding and rearrangement of the nucleotide-binding cleft, which is vital for actin to reach its native state. The differences in the chemical properties of the actin-GroEL and the actin-TRiC complexes were also determined by measurements of fluorescein anisotropies and AEDANS emission shifts for probes attached to positions spread throughout the actin structure.The evolutionary aspects of the chaperonin mechanisms and the target protein binding were further investigated in another study. In this study, the prokaryotic homologue to actin, MreB, was shown to bind to both TRiC and GroEL. MreB was also shown to bind to the co-chaperonin GroES.In a separate study, the interaction between actin and the chaperone prefoldin was investigated. In vivo prefoldin interacts with non-native actin and transfers it to TRiC for subsequent and proper folding. In this homo-FRET study, it was shown that actin binds to prefoldin in a stretched conformation, similar to the initial binding of actin to TRiC.
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