| 1. |
- Bosco, Daryl A, et al.
(författare)
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Dissecting the microscopic steps of the cyclophilin a enzymatic cycle on the biological substrate HIV-capsid by NMR
- 2010
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Ingår i: Journal of Molecular Biology. - : Elsevier. - 0022-2836 .- 1089-8638. ; 403:5, s. 723-38
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Tidskriftsartikel (refereegranskat)abstract
- Peptidyl-prolyl isomerases (PPIases) are emerging as key regulators of many diverse biological processes. Elucidating the role of PPIase activity in vivo has been challenging because mutagenesis of active site residues not only reduces the catalytic activity of these enzymes, but also dramatically affects substrate binding. Employing the cyclophilin A (CypA) PPIase together with its biologically relevant and natively folded substrate, the N-terminal domain of the HIV-1 capsid (CA(N)) protein, we demonstrate here how to dissect residue specific contributions to PPIase catalysis versus substrate binding utilizing NMR spectroscopy. Surprisingly, a number of CypA active-site mutants previously assumed to be strongly diminished in activity toward biological substrates based on a peptide assay only, catalyze the HIV capsid with wild-type activity, but with a change in the rate-limiting step of the enzymatic cycle. The results illustrate that a quantitative analysis of catalysis using the biological substrates is critical when interpreting the effects of PPIase mutations in biological assays.
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| 2. |
- Cabrera, Yovana, 1987, et al.
(författare)
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Fine-tuning of the Hsc70-based Human Protein Disaggregase Machinery by the Distinctive C-terminal Extension of Apg2
- 2022
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Ingår i: JOURNAL OF MOLECULAR BIOLOGY. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 434:22
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Tidskriftsartikel (refereegranskat)abstract
- Apg2, one of the three cytosolic Hsp110 chaperones in humans, supports reactivation of unordered and ordered protein aggregates by Hsc70 (HspA8). Together with DnaJB1, Apg2 serves to nucleate Hsc70 molecules into sites where productive entropic pulling forces can be developed. During aggregate reac-tivation, Apg2 performs as a specialized nucleotide exchange factor, but the origin of its specialization is poorly defined. Here we report on the role of the distinctive C-terminal extension present in Apg2 and other metazoan homologs. We found that the first part of this Apg2 subdomain, with propensity to adopt a-helical structure, interacts with the nucleotide binding domain of Hsc70 in a nucleotide -dependent manner, contributing significantly to the stability of the Hsc70:Apg2 complex. Moreover, the second intrinsically disordered segment of Apg2 C-terminal extension plays an important role as a down -regulator of nucleotide exchange. An NMR analysis showed that the interaction with Hsc70 nucleotide binding domain modifies the chemical environment of residues located in important functional sites such as the interface between lobe I and II and the nucleotide binding site. Our data indicate that Apg2 C -terminal extension is a fine-tuner of human Hsc70 activity that optimizes the substrate remodeling ability of the chaperone system.
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| 3. |
- Eisenmesser, Elan Z, et al.
(författare)
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Intrinsic dynamics of an enzyme underlies catalysis
- 2005
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 438, s. 117-21
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Tidskriftsartikel (refereegranskat)abstract
- A unique feature of chemical catalysis mediated by enzymes is that the catalytically reactive atoms are embedded within a folded protein. Although current understanding of enzyme function has been focused on the chemical reactions and static three-dimensional structures, the dynamic nature of proteins has been proposed to have a function in catalysis1, 2, 3, 4, 5. The concept of conformational substates has been described6; however, the challenge is to unravel the intimate linkage between protein flexibility and enzymatic function. Here we show that the intrinsic plasticity of the protein is a key characteristic of catalysis. The dynamics of the prolyl cis–trans isomerase cyclophilin A (CypA) in its substrate-free state and during catalysis were characterized with NMR relaxation experiments. The characteristic enzyme motions detected during catalysis are already present in the free enzyme with frequencies corresponding to the catalytic turnover rates. This correlation suggests that the protein motions necessary for catalysis are an intrinsic property of the enzyme and may even limit the overall turnover rate. Motion is localized not only to the active site but also to a wider dynamic network. Whereas coupled networks in proteins have been proposed previously3, 7, 8, 9, 10, we experimentally measured the collective nature of motions with the use of mutant forms of CypA. We propose that the pre-existence of collective dynamics in enzymes before catalysis is a common feature of biocatalysts and that proteins have evolved under synergistic pressure between structure and dynamics.
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| 4. |
- Masoodi, Mojgan, et al.
(författare)
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Metabolomics and lipidomics in NAFLD : biomarkers and non-invasive diagnostic tests
- 2021
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Ingår i: Nature Reviews. Gastroenterology & Hepatology. - : Nature Publishing Group. - 1759-5045 .- 1759-5053. ; 18:12, s. 835-856
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Forskningsöversikt (refereegranskat)abstract
- Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver diseases worldwide and is often associated with aspects of metabolic syndrome. Despite its prevalence and the importance of early diagnosis, there is a lack of robustly validated biomarkers for diagnosis, prognosis and monitoring of disease progression in response to a given treatment. In this Review, we provide an overview of the contribution of metabolomics and lipidomics in clinical studies to identify biomarkers associated with NAFLD and nonalcoholic steatohepatitis (NASH). In addition, we highlight the key metabolic pathways in NAFLD and NASH that have been identified by metabolomics and lipidomics approaches and could potentially be used as biomarkers for non-invasive diagnostic tests. Overall, the studies demonstrated alterations in amino acid metabolism and several aspects of lipid metabolism including circulating fatty acids, triglycerides, phospholipids and bile acids. Although we report several studies that identified potential biomarkers, few have been validated.
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| 5. |
- Qvist, Johan, et al.
(författare)
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Hydration Dynamics of a Halophilic Protein in Folded and Unfolded States
- 2012
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 116:10, s. 3436-3444
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Tidskriftsartikel (refereegranskat)abstract
- Proteins from halophilic microorganisms thriving at high salinity have an excess of charged carboxylate groups, and it is widely believed that this gives rise to an exceptionally strong hydration that stabilizes these proteins against unfolding and aggregation. Here, we examine this hypothesis by characterizing the hydration dynamics of a halophilic model protein with frequency- and temperature-dependent O-17 magnetic relaxation. The halophilic protein Kx6E was constructed by replacing six lysine residues with glutamate residues in the IgG binding domain of protein L. We also studied the unfolded form of Kx6E in the absence of salt. We find that the hydration dynamics of Kx6E does not differ from protein L or from other previously studied mesophilic proteins. This finding challenges the hypothesis of exceptional hydration for halophilic proteins. The unfolded form of Kx6E is found to be expanded, with a weaker dynamical perturbation of the hydration water than for folded proteins.
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