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- 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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| 2. |
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| 3. |
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| 4. |
- Korzhnev, Dmitry M., et al.
(författare)
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The folding pathway of an FF domain : Characterization of an on-pathway intermediate state under folding conditions by N-15, C-13(alpha) and C-13-methyl relaxation dispersion and H-1/(2) H-exchange NMR Spectroscopy
- 2007
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Ingår i: Journal of Molecular Biology. - : Elsevier. - 0022-2836 .- 1089-8638. ; 372:2, s. 497-512
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Tidskriftsartikel (refereegranskat)abstract
- The FF domain from the human protein HYPA/FBP11 folds via a lowenergy on-pathway intermediate (. Elucidation of the structure of such folding intermediates and denatured states under conditions that favour folding are difficult tasks. Here, we investigated the millisecond time-scale equilibrium folding transition of the 71-residue four-helix bundle wild-type protein by N-15, C-13(alpha) and methyl C-13 Carr-Purcell-Meiboom-Gill (CPMG) NMR relaxation dispersion experiments and by H-exchange measurements. The relaxation data for the wild-type protein fitted a simple two-site exchange process between the folded state (F) and I. Destabilization of F in mutants A17G and Q19G allowed the detection of the unfolded state U by 15N CPMG relaxation dispersion. The dispersion data for these mutants fitted a three-site exchange scheme, U-I-F, with I populated higher than U. The kinetics and thermodynamics of the folding reaction were obtained via temperature and urea-dependent relaxation dispersion experiments, along with structural information on I from backbone N-15, C-13(alpha) and side-chain methyl 13C chemical shifts, with further information from protection factors for the backbone amide groups from H-1/(2) H-exchange. Notably, helices H1-H3 are at least partially formed in 1, while helix H4 is largely disordered. Chemical shift differences for the methyl 13 C nuclei suggest a paucity of stable, native-like hydrophobic interactions in 1. These data are consistent with (D-analysis of the rate-limiting transition state between I and F. The combination of relaxation dispersion and (1) data can elucidate whole experimental folding pathways.
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| 5. |
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| 6. |
- Zhuravleva, Anastasia, 1979, et al.
(författare)
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Gated electron transfers and electron pathways in azurin: a NMR dynamic study at multiple fields and temperatures.
- 2004
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Ingår i: Journal of molecular biology. - : Elsevier BV. - 0022-2836. ; 342:5, s. 1599-611
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic properties of electron transfer pathways in a small blue copper cupredoxin are explored using an extensive 15N NMR relaxation study of reduced Pseudomonas aeruginosa azurin at four magnetic fields (500-900 MHz) and at two temperatures chosen well below the melting point of the protein. Following a careful model-free analysis, several protein regions with different dynamic regimes are identified. Nanosecond time-scale mobility characterizes various residues of the hydrophobic surface patch believed to mark the natural entry point for electrons, notably the surface-exposed copper-ligand His117. These findings are consistent with a gated electron transfer process according to the "dynamic docking" model. Residues 47-49 along intramolecular pathways of electrons show rigidity that is remarkably conserved when increasing the temperature. Three different conformational exchange processes were observed in the millisecond range, one near the only disulfide bridge in the molecule and two near the copper ion. The latter two processes are consistent with previous data such as crystal structures at various pH values and NMR relaxation dispersion experiments; they may indicate an additional gated electron transfer mechanism at slower time-scales.
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| 7. |
- Zhuravleva, Anastasia, 1979, et al.
(författare)
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Propagation of dynamic changes in barnase upon binding of barstar: an NMR and computational study.
- 2007
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Ingår i: Journal of molecular biology. - : Elsevier BV. - 0022-2836. ; 367:4, s. 1079-92
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Tidskriftsartikel (refereegranskat)abstract
- NMR spectroscopy and computer simulations were used to examine changes in chemical shifts and in dynamics of the ribonuclease barnase that result upon binding to its natural inhibitor barstar. Although the spatial structures of free and bound barnase are very similar, binding results in changes of the dynamics of both fast side-chains, as revealed by (2)H relaxation measurements, and NMR chemical shifts in an extended beta-sheet that is located far from the binding interface. Both side-chain dynamics and chemical shifts are sensitive to variations in the ensemble populations of the inter-converting molecular states, which can escape direct structural observation. Molecular dynamics simulations of free barnase and barnase in complex with barstar, as well as a normal mode analysis of barnase using a Gaussian network model, reveal relatively rigid domains that are separated by the extended beta-sheet mentioned above. The observed changes in NMR parameters upon ligation can thus be rationalized in terms of changes in inter-domain dynamics and in populations of exchanging states, without measurable structural changes. This provides an alternative model for the propagation of a molecular response to ligand binding across a protein that is based exclusively on changes in dynamics.
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