| 1. |
- Calosci, Nicoletta, et al.
(författare)
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Comparison of successive transition states for folding reveals alternative early folding pathways of two homologous proteins
- 2008
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : The National Academy of Sciences of the USA. - 0027-8424 .- 1091-6490. ; 105:49, s. 19241-19246
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Tidskriftsartikel (refereegranskat)abstract
- The energy landscape theory provides a general framework for describing protein folding reactions. Because a large number of studies, however, have focused on two-state proteins with single well-defined folding pathways and without detectable intermediates, the extent to which free energy landscapes are shaped up by the native topology at the early stages of the folding process has not been fully characterized experimentally. To this end, we have investigated the folding mechanisms of two homologous three-state proteins, PTP-BL PDZ2 and PSD-95 PDZ3, and compared the early and late transition states on their folding pathways. Through a combination of Phi value analysis and molecular dynamics simulations we obtained atomic-level structures of the transition states of these homologous three-state proteins and found that the late transition states are much more structurally similar than the early ones. Our findings thus reveal that, while the native state topology defines essentially in a unique way the late stages of folding, it leaves significant freedom to the early events, a result that reflects the funneling of the free energy landscape toward the native state.
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| 2. |
- Blombach, Fabian, et al.
(författare)
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Archaeal MBF1 binds to 30S and 70S ribosomes via its helix-turn-helix domain
- 2014
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 462, s. 373-384
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Tidskriftsartikel (refereegranskat)abstract
- MBF1 (multi-protein bridging factor 1) is a protein containing a conserved HTH (helix-turn-helix) domain in both eukaryotes and archaea. Eukaryotic MBF1 has been reported to function as a transcriptional co-activator that physically bridges transcription regulators with the core transcription initiation machinery of RNA polymerase II. In addition, MBF1 has been found to be associated with polyadenylated mRNA in yeast as well as in mammalian cells. aMBF1 (archaeal MBF1) is very well conserved among most archaeal lineages; however, its function has so far remained elusive. To address this, we have conducted a molecular characterization of this aMBF1. Affinity purification of interacting proteins indicates that aMBF1 binds to ribosomal subunits. On sucrose density gradients, aMBF1 co-fractionates with free 30S ribosomal subunits as well as with 70S ribosomes engaged in translation. Binding of aMBF1 to ribosomes does not inhibit translation. Using NMR spectroscopy, we show that aMBF1 contains a long intrinsically disordered linker connecting the predicted N-terminal zinc-ribbon domain with the C-terminal HTH domain. The HTH domain, which is conserved in all archaeal and eukaryotic MBF1 homologues, is directly involved in the association of aMBF1 with ribosomes. The disordered linker of the ribosome-bound aMBF1 provides the N-terminal domain with high flexibility in the aMBF1 ribosome complex. Overall, our findings suggest a role for aMBF1 in the archaeal translation process.
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| 3. |
- Hultqvist, Greta, 1980-, et al.
(författare)
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Emergence and evolution of an interaction between intrinsically disordered proteins
- 2017
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Ingår i: eLIFE. - 2050-084X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Protein-protein interactions involving intrinsically disordered proteins are important for cellular function and common in all organisms. However, it is not clear how such interactions emerge and evolve on a molecular level. We performed phylogenetic reconstruction, resurrection and biophysical characterization of two interacting disordered protein domains, CID and NCBD. CID appeared after the divergence of protostomes and deuterostomes 450-600 million years ago, while NCBD was present in the protostome/deuterostome ancestor. The most ancient CID/NCBD formed a relatively weak complex (K(d similar to)5 mu M). At the time of the first vertebrate-specific whole genome duplication, the affinity had increased (K-d\similar to 200 nM) and was maintained in further speciation. Experiments together with molecular modeling using NMR chemical shifts suggest that new interactions involving intrinsically disordered proteins may evolve via a low-affinity complex which is optimized by modulating direct interactions as well as dynamics, while tolerating several potentially disruptive mutations.
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| 4. |
- Karlsson, Elin, et al.
(författare)
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A structurally heterogeneous transition state underlies coupled binding and folding of disordered proteins
- 2019
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 294:4, s. 1230-1239
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Tidskriftsartikel (refereegranskat)abstract
- Many intrinsically disordered proteins (IDPs) attain a well-defined structure in a coupled folding and binding reaction with another protein. Such reactions may involve early to late formation of different native structural regions along the reaction pathway. To obtain insights into the transition state for a coupled binding and folding reaction, we performed restrained molecular dynamics simulations using previously determined experimental binding phi(b) values of the interaction between two IDP domains: the activation domain from the p160 transcriptional co-activator for thyroid hormone and retinoid receptors (ACTR) and the nuclear co-activator binding domain (NCBD) of CREB-binding protein, each forming three well-defined alpha-helices upon binding. These simulations revealed that both proteins are largely disordered in the transition state for complex formation, except for two helices, one from each domain, that display a native-like structure. The overall transition state structure was extended and largely dynamic with many weakly populated contacts. To test the transition state model, we combined site-directed mutagenesis with kinetic experiments, yielding results consistent with overall diffuse interactions and formation of native intramolecular interactions in the third NCBD helix during the binding reaction. Our findings support the view that the transition state and, by inference, any encounter complex in coupled binding and folding reactions are structurally heterogeneous and largely independent of specific interactions. Furthermore, experimental phi(b) values and Bronsted plots suggested that the transition state is globally robust with respect to most mutations but can display more native-like features for some highly destabilizing mutations, possibly because of Hammond behavior or ground-state effects.
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| 5. |
- Karlsson, Elin, et al.
(författare)
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Disordered Regions Flanking the Binding Interface Modulate Affinity between CBP and NCOA
- 2022
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Ingår i: Journal of Molecular Biology. - : Elsevier. - 0022-2836 .- 1089-8638. ; 434:13
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Tidskriftsartikel (refereegranskat)abstract
- Recognition motifs that mediate protein-protein interactions are usually embedded within longer intrinsically disordered regions. While binding interfaces involving the recognition motif in such interactions are well studied, less is known about the role of disordered regions flanking the motifs. The interaction between the transcriptional co-activators NCOA3 (ACTR) and CBP is mediated by coupled binding and folding of the two domains CID and NCBD. Here, we used circular dichroism and kinetics to directly quantify the contribution of the adjacent flanking regions of CID to its interaction with NCBD. Using N-and C terminal combinatorial variants we found that the flanking regions promote binding in an additive fashion while retaining a large degree of disorder in the complex. Experiments at different ionic strengths demonstrated that the increase in affinity is not mediated by electrostatic interactions from the flanking regions. Instead, site-directed mutagenesis and molecular dynamics simulations suggest that binding is promoted by short-lived non-specific hydrophobic contacts between the flanking regions and NCBD. Our findings are consistent with highly frustrated interactions outside of the canonical binding interface resulting in a slightly energetically favorable fuzzy binding. Modulation of affinity via flanking regions could represent a general mechanism for functional regulation by intrinsically disordered protein regions.(c) 2022 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
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| 6. |
- Karlsson, Elin, et al.
(författare)
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Mapping the transition state for a binding reaction between ancient intrinsically disordered proteins
- 2020
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Ingår i: Journal of Biological Chemistry. - : AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC. - 0021-9258 .- 1083-351X. ; 295:51, s. 17698-17712
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Tidskriftsartikel (refereegranskat)abstract
- Intrinsically disordered protein domains often have multiple binding partners. It is plausible that the strength of pairing with specific partners evolves from an initial low affinity to a higher affinity. However, little is known about the molecular changes in the binding mechanism that would facilitate such a transition. We previously showed that the interaction between two intrinsically disordered domains, NCBD and CID, likely emerged in an ancestral deuterostome organism as a low-affinity interaction that subsequently evolved into a higher-affinity interaction before the radiation of modern vertebrate groups. Here we map native contacts in the transition states of the low-affinity ancestral and high-affinity human NCBD/CID interactions. We show that the coupled binding and folding mechanism is overall similar but with a higher degree of native hydrophobic contact formation in the transition state of the ancestral complex and more heterogeneous transient interactions, including electrostatic pairings, and an increased disorder for the human complex. Adaptation to new binding partners may be facilitated by this ability to exploit multiple alternative transient interactions while retaining the overall binding and folding pathway.
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| 7. |
- Kukic, Predrag, et al.
(författare)
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Structural Insights into the Calcium-Mediated Allosteric Transition in the C-Terminal Domain of Calmodulin from Nuclear Magnetic Resonance Measurements
- 2016
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Ingår i: Biochemistry. - : AMER CHEMICAL SOC. - 0006-2960 .- 1520-4995. ; 55:1, s. 19-28
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Tidskriftsartikel (refereegranskat)abstract
- Calmodulin is a two-domain signaling protein that becomes activated upon binding cooperatively two pairs of calcium ions, leading to large-scale conformational changes that expose its binding site. Despite significant advances in understanding the structural biology of calmodulin functions, the mechanistic details of the conformational transition between closed and open states have remained unclear. To investigate this transition, we used a combination of molecular dynamics simulations and nuclear magnetic resonance (NMR) experiments on the Ca2+-saturated E140Q C-terminal domain variant. Using chemical shift restraints in replica-averaged metadynamics simulations, we obtained a high-resolution structural ensemble consisting of two conformational states and validated such an ensemble against three independent experimental data sets, namely, interproton nuclear Overhauser enhancements, N-15 order parameters, and chemical shift differences between the exchanging states. Through a detailed analysis of this structural ensemble and of the corresponding statistical weights, we characterized a calcium-mediated conformational transition whereby the coordination of Ca2+ by just one oxygen of the bidentate ligand E140 triggers a concerted movement of the two EF-hands that exposes the target binding site. This analysis provides atomistic insights into a possible Ca2+-mediated activation mechanism of calmodulin that cannot be achieved from static structures alone or from ensemble NMR measurements of the transition between conformations.
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| 8. |
- Sala, Benedetta Maria, et al.
(författare)
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Conformational Stability and Dynamics in Crystals Recapitulate Protein Behavior in Solution
- 2020
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Ingår i: Biophysical Journal. - : Ceii Press. - 0006-3495 .- 1542-0086. ; 119:5, s. 978-988
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Tidskriftsartikel (refereegranskat)abstract
- A growing body of evidences has established that in many cases proteins may preserve most of their function and flexibility in a crystalline environment, and several techniques are today capable to characterize molecular properties of proteins in tightly packed lattices. Intriguingly, in the case of amyloidogenic precursors, the presence of transiently populated states (hidden to conventional crystallographic studies) can be correlated to the pathological fate of the native fold; the low fold stability of the native state is a hallmark of aggregation propensity. It remains unclear, however, to which extent biophysical properties of proteins such as the presence of transient conformations or protein stability characterized in crystallo reflect the protein behavior that is more commonly studied in solution. Here, we address this question by investigating some biophysical properties of a prototypical amyloidogenic system, beta 2-microglobulin in solution and in microcrystalline state. By combining NMR chemical shifts with molecular dynamics simulations, we confirmed that conformational dynamics of beta 2-microglobulin native state in the crystal lattice is in keeping with what observed in solution. A comparative study of protein stability in solution and in crystallo is then carried out, monitoring the change in protein secondary structure at increasing temperature by Fourier transform infrared spectroscopy. The increased structural order of the crystalline state contributes to provide better resolved spectral components compared to those collected in solution and crucially, the crystalline samples display thermal stabilities in good agreement with the trend observed in solution. Overall, this workshows that protein stability and occurrence of pathological hidden states in crystals parallel their solution counterpart, confirming the interest of crystals as a platform for the biophysical characterization of processes such as unfolding and aggregation.
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