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Akhtar A, Rashid U, Seth C, Kumar S, Broekmann P, Kaliginedi V. Modulating the charge transport in metal│molecule│metal junctions via electrochemical gating. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.138540] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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2
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Unfolding cytochromes c-b 562 and Rd apo b 562. J Inorg Biochem 2020; 211:111209. [PMID: 32818710 DOI: 10.1016/j.jinorgbio.2020.111209] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 07/26/2020] [Accepted: 07/28/2020] [Indexed: 11/22/2022]
Abstract
We have analyzed the early stages of unfolding of cytochromes c-b562 (PDB ID: 2BC5) and Rd apo b562 (PDB ID: 1YYJ). Our geometrical approach proceeds from an analysis of the crystal structure reported for each protein. We quantify, residue-by-residue and region-by-region, the spatial and angular changes in the structure as the protein denatures, and quantify differences that result from the seven residues that differ in the two proteins. Using two independent analyses, one based on spatial metrics and the second on angular metrics, we establish the order of unfolding of the five helices in cyt c-b562 and the four helices in the apo protein. For the two helices nearest the N-terminal end of both proteins, the ones in the apo protein unfold first. For the two helices nearest the C-terminal end, the interior helix of the apo protein unfolds first, whereas the terminal helix of the holo protein unfolds first. Excluded-volume effects (repulsive interactions) are minimized in turning regions; the overall range in Δ values is Δ = 36.3 Å3 for cyt c-b562 and Δ = 36.6 Å3 for the apo protein, whereas the span for all 20 amino acids is Δ = 167.7 Å3. As our work indicates that the interior helix of cytochrome c-b562 is the first to fold, we suggest that this helix protects the heme from misligation, consistent with ultrafast folding over a minimally frustrated funneled landscape.
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Dillinger S, Lang J, Niedner-Schatteburg G. Cryo IR Spectroscopy of [Hemin] + Complexes in Isolation. J Phys Chem A 2017; 121:7191-7196. [PMID: 28876926 DOI: 10.1021/acs.jpca.7b08604] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We present cryo IR spectra of isolated [Hemin]+ adducts with CO, N2, and O2 ([Hemin(CO)1]+, [Hemin(CO)2]+, [Hemin(14N2)]+, [Hemin(15N2)]+, and [Hemin(O2)]+). Well resolved bands allow for the elucidation of structure and spin multiplicity in conjunction with density functional (DFT) calculations. There is a quartet spin state for the N2 and CO adducts and a sextet spin state for the O2 adduct, where the O2 retains its triplet state. The double CO adsorption induces significant changes in the vibrational patterns of the IR spectra, which we take as strong evidence for a spin quenching into a doublet. Our study characterizes [Hemin]+, which is the Fe3+ oxidation product of heme that is of ubiquitous presence in hemeproteins.
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Affiliation(s)
- Sebastian Dillinger
- Fachbereich Chemie and Forschungszentrum OPTIMAS, TU Kaiserslautern , 67663 Kaiserslautern, Germany
| | - Johannes Lang
- Fachbereich Chemie and Forschungszentrum OPTIMAS, TU Kaiserslautern , 67663 Kaiserslautern, Germany
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Miyamoto T, Kuribayashi M, Nagao S, Shomura Y, Higuchi Y, Hirota S. Domain-swapped cytochrome cb562 dimer and its nanocage encapsulating a Zn-SO 4 cluster in the internal cavity. Chem Sci 2015; 6:7336-7342. [PMID: 28791095 PMCID: PMC5519777 DOI: 10.1039/c5sc02428e] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 09/22/2015] [Indexed: 01/01/2023] Open
Abstract
Three domain-swapped cytochrome cb562 dimers formed a unique cage structure with a Zn–SO4 cluster inside the cavity.
Protein nanostructures have been gaining in interest, along with developments in new methods for construction of novel nanostructures. We have previously shown that c-type cytochromes and myoglobin form oligomers by domain swapping. Herein, we show that a four-helix bundle protein cyt cb562, with the cyt b562 heme attached to the protein moiety by two Cys residues insertion, forms a domain-swapped dimer. Dimeric cyt cb562 did not dissociate to monomers at 4 °C, whereas dimeric cyt b562 dissociated under the same conditions, showing that heme attachment to the protein moiety stabilizes the domain-swapped structure. According to X-ray crystallographic analysis of dimeric cyt cb562, the two helices in the N-terminal region of one protomer interacted with the other two helices in the C-terminal region of the other protomer, where Lys51–Asp54 served as a hinge loop. The heme coordination structure of the dimer was similar to that of the monomer. In the crystal, three domain-swapped cyt cb562 dimers formed a unique cage structure with a Zn–SO4 cluster inside the cavity. The Zn–SO4 cluster consisted of fifteen Zn2+ and seven SO42– ions, whereas six additional Zn2+ ions were detected inside the cavity. The cage structure was stabilized by coordination of the amino acid side chains of the dimers to the Zn2+ ions and connection of two four-helix bundle units through the conformation-adjustable hinge loop. These results show that domain swapping can be applied in the construction of unique protein nanostructures.
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Affiliation(s)
- Takaaki Miyamoto
- Graduate School of Materials Science , Nara Institute of Science and Technology , 8916-5 Takayama, Ikoma , Nara 630-0192 , Japan .
| | - Mai Kuribayashi
- Graduate School of Materials Science , Nara Institute of Science and Technology , 8916-5 Takayama, Ikoma , Nara 630-0192 , Japan .
| | - Satoshi Nagao
- Graduate School of Materials Science , Nara Institute of Science and Technology , 8916-5 Takayama, Ikoma , Nara 630-0192 , Japan .
| | - Yasuhito Shomura
- Graduate School of Science and Engineering , Ibaraki University , 4-12-1, Nakanarusawa , Hitachi , Ibaraki 316-8511 , Japan
| | - Yoshiki Higuchi
- Department of Life Science , Graduate School of Life Science , University of Hyogo , 3-2-1 Koto, Kamigori-cho, Ako-gun , Hyogo 678-1297 , Japan.,RIKEN SPring-8 Center , 1-1-1 Koto, Sayo-cho, Sayo-gun , Hyogo 679-5148 , Japan
| | - Shun Hirota
- Graduate School of Materials Science , Nara Institute of Science and Technology , 8916-5 Takayama, Ikoma , Nara 630-0192 , Japan .
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Schaller A, Connors NK, Dwyer MD, Oelmeier SA, Hubbuch J, Middelberg APJ. Computational study of elements of stability of a four-helix bundle protein biosurfactant. J Comput Aided Mol Des 2014; 29:47-58. [PMID: 25323391 DOI: 10.1007/s10822-014-9803-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 10/10/2014] [Indexed: 10/24/2022]
Abstract
Biosurfactants are surface-active molecules produced principally by microorganisms. They are a sustainable alternative to chemically-synthesized surfactants, having the advantages of being non-toxic, highly functional, eco-friendly and biodegradable. However they are currently only used in a few industrial products due to costs associated with production and purification, which exceed those for commodity chemical surfactants. DAMP4, a member of a four-helix bundle biosurfactant protein family, can be produced in soluble form and at high yield in Escherichia coli, and can be recovered using a facile thermal phase-separation approach. As such, it encompasses an interesting synergy of biomolecular and chemical engineering with prospects for low-cost production even for industrial sectors. DAMP4 is highly functional, and due to its extraordinary thermal stability it can be purified in a simple two-step process, in which the combination of high temperature and salt leads to denaturation of all contaminants, whereas DAMP4 stays stable in solution and can be recovered by filtration. This study aimed to characterize and understand the fundamental drivers of DAMP4 stability to guide further process and surfactant design studies. The complementary use of experiments and molecular dynamics simulation revealed a broad pH and temperature tolerance for DAMP4, with a melting point of 122.4 °C, suggesting the hydrophobic core as the major contributor to thermal stability. Simulation of systematically created in silico variants of DAMP4 showed an influence of number and location of hydrophilic mutations in the hydrophobic core on stability, demonstrating a tolerance of up to three mutations before a strong loss in stability occurred. The results suggest a consideration of a balance of stability, functionality and kinetics for new designs according to their application, aiming for maximal functionality but at adequate stability to allow for cost-efficient production using thermal phase separation approaches.
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Affiliation(s)
- Andrea Schaller
- Centre for Biomolecular Engineering, Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD, 4072, Australia
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Bouley Ford ND, Shin DW, Gray HB, Winkler JR. Intrachain contact dynamics in unfolded cytochrome cb562. J Phys Chem B 2013; 117:13206-11. [PMID: 23992117 DOI: 10.1021/jp403234h] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have investigated intrachain contact dynamics in unfolded cytochrome cb562 by monitoring heme quenching of excited ruthenium photosensitizers covalently bound to residues along the polypeptide. Intrachain diffusion for chemically denatured proteins proceeds on the microsecond time scale with an upper limit of 0.1 μs. The rate constants exhibit a power-law dependence on the number of peptide bonds between the heme and Ru complex. The power-law exponent of -1.5 is consistent with theoretical models for freely jointed Gaussian chains, but its magnitude is smaller than that reported for several synthetic polypeptides. Contact formation within a stable loop was examined in a His63-heme ligated form of the protein under denaturing conditions. Loop formation accelerated contact kinetics for the Ru66 labeling site, owing to reduction in the length of the peptide separating redox sites. For other labeling sites within the stable loop, quenching rates were modestly reduced compared to the open chain polymer.
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Affiliation(s)
- Nicole D Bouley Ford
- Beckman Institute, California Institute of Technology , Pasadena, California 91125, United States
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7
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Abstract
We have investigated the folding dynamics of Thermus thermophilus cytochrome c(552) by time-resolved fluorescence energy transfer between the heme and each of seven site-specific fluorescent probes. We have found both an equilibrium unfolding intermediate and a distinct refolding intermediate from kinetics studies. Depending on the protein region monitored, we observed either two-state or three-state denaturation transitions. The unfolding intermediate associated with three-state folding exhibited native contacts in β-sheet and C-terminal helix regions. We probed the formation of a refolding intermediate by time-resolved fluorescence energy transfer between residue 110 and the heme using a continuous flow mixer. The intermediate ensemble, a heterogeneous mixture of compact and extended polypeptides, forms in a millisecond, substantially slower than the ∼100-μs formation of a burst-phase intermediate in cytochrome c. The surprising finding is that, unlike for cytochrome c, there is an observable folding intermediate, but no microsecond burst phase in the folding kinetics of the structurally related thermostable protein.
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Pia EAD, Chi Q, Jones DD, Macdonald JE, Ulstrup J, Elliott M. Single-molecule mapping of long-range electron transport for a cytochrome b(562) variant. NANO LETTERS 2011; 11:176-182. [PMID: 21105644 DOI: 10.1021/nl103334q] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Cytochrome b(562) was engineered to introduce a cysteine residue at a surface-exposed position to facilitate direct self-assembly on a Au(111) surface. The confined protein exhibited reversible and fast electron exchange with a gold substrate over a distance of 20 Å between the heme redox center and the gold surface, a clear indication that a long-range electron-transfer pathway is established. Electrochemical scanning tunneling microscopy was used to map electron transport features of the protein at the single-molecule level. Tunneling resonance was directly imaged and apparent molecular conductance was measured, which both show strong redox-gated effects. This study has addressed the first case of heme proteins and offered new perspectives in single-molecule bioelectronics.
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Affiliation(s)
- Eduardo Antonio Della Pia
- School of Physics and Astronomy, Cardiff University, Queens's Building, The Parade, Cardiff CF24 3AA, U.K
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Edwards WR, Williams AJ, Morris JL, Baldwin AJ, Allemann RK, Jones DD. Regulation of β-Lactamase Activity by Remote Binding of Heme: Functional Coupling of Unrelated Proteins through Domain Insertion. Biochemistry 2010; 49:6541-9. [DOI: 10.1021/bi100793y] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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Lin YW, Nie CM, Liao LF. Folding behaviors of apocytochrome b5 and its mutants: Insights from high temperature molecular dynamics simulations. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/j.theochem.2009.06.036] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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12
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Abstract
Cytochrome cb(562) is a variant of an Escherichia coli four-helix bundle b-type heme protein in which the porphyrin prosthetic group is covalently ligated to the polypeptide near the terminus of helix 4. Studies from other laboratories have shown that the apoprotein folds rapidly without the formation of intermediates, whereas the holoprotein loses heme before native structure can be attained. Time-resolved fluorescence energy transfer (TRFET) measurements of cytochrome cb(562) refolding triggered using an ultrafast continuous-flow mixer (150 micros dead time) reveal that heme attachment to the polypeptide does not interfere with rapid formation of the native structure. Analyses of the TRFET data produce distributions of Trp-59-heme distances in the protein before, during, and after refolding. Characterization of the moments and time evolution of these distributions provides compelling evidence for a refolding mechanism that does not involve significant populations of intermediates. These observations suggest that the cytochrome b(562) folding energy landscape is minimally frustrated and able to tolerate the introduction of substantial perturbations (i.e., the heme prosthetic group) without the formation of deep misfolded traps.
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Lin YW, Ni FY, Ying TL. Early events in thermal unfolding of apocytochrome b562 and its double-cysteine mutant as revealed by molecular dynamics simulation. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/j.theochem.2008.07.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Nguyen H, Jäger M, Kelly JW, Gruebele M. Engineering a beta-sheet protein toward the folding speed limit. J Phys Chem B 2007; 109:15182-6. [PMID: 16852923 DOI: 10.1021/jp052373y] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent experimental studies have shown that alpha-helical proteins can approach the folding "speed limit", where folding switches from an activated to a downhill process in free energy. beta-sheet proteins are generally thought to fold more slowly than helix bundles. However, based on studies of hairpins, folding should still be able to approach the microsecond time scale. Here we demonstrate how the hPin1 WW domain, a triple-stranded beta-sheet protein with a sharp thermodynamic melting transition, can be engineered toward the folding "speed limit" without a significant loss in thermal denaturation cooperativity.
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15
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Pletneva EV, Zhao Z, Kimura T, Petrova KV, Gray HB, Winkler JR. Probing the cytochrome c' folding landscape. J Inorg Biochem 2007; 101:1768-75. [PMID: 17673297 PMCID: PMC2110879 DOI: 10.1016/j.jinorgbio.2007.06.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Revised: 05/31/2007] [Accepted: 06/01/2007] [Indexed: 11/27/2022]
Abstract
The folding kinetics of R. palustris cytochrome c' (cyt c') have been monitored by heme absorption and native Trp72 fluorescence at pH 5. The Trp72 fluorescence burst signal suggests early compaction of the polypeptide ensemble. Analysis of heme transient absorption spectra reveals deviations from two-state behavior, including a prominent slow phase that is accelerated by the prolyl isomerase cyclophilin. A nonnative proline configuration (Pro21) likely interferes with the formation of the helical bundle surrounding the heme.
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Affiliation(s)
| | | | | | | | - Harry B. Gray
- *Corresponding authors. E-mails: (H.B.G.) and (J.R.W.)
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16
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Dreher C, Prodöhl A, Weber M, Schneider D. Heme binding properties of heterologously expressed spinach cytochromeb6: Implications for transmembraneb-type cytochrome formation. FEBS Lett 2007; 581:2647-51. [PMID: 17511988 DOI: 10.1016/j.febslet.2007.05.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2007] [Revised: 04/25/2007] [Accepted: 05/02/2007] [Indexed: 11/17/2022]
Abstract
In vivo and in vitro requirements for the formation of cytochrome b(6) were examined to analyze the mechanisms of transmembrane b-type cytochrome formation. After heterologous expression of spinach cytochrome b(6), formation of the holo-cytochrome was observed within the E. coli inner membrane. The transmembrane orientation of cytochrome b(6) appeared not to be critical for heme binding and holo-cytochrome formation. Furthermore, in vitro reconstitution of cytochrome b(6) was possible under oxidizing as well as under reducing conditions. Taken together these observations strongly indicate that transmembrane b-type cytochromes can spontaneously assemble in vitro as well as in a membrane.
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Affiliation(s)
- Carolin Dreher
- Institut für Biochemie und Molekularbiologie, Zentrum für Biochemie und Molekulare Zellforschung, Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Strasse 19, Freiburg, Germany
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17
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Abstract
We studied conformational stability and folding kinetics of a three-stranded beta-sheet containing two rigid turns. Static infrared measurements indicate that this beta-sheet undergoes a broad but cooperative thermal unfolding transition with a midpoint at approximately 53 degrees C. Interestingly, time-resolved infrared experiments show that its relaxation kinetics in response to a temperature-jump (T-jump) occur on the nanosecond time scale (e.g., the relaxation time is approximately 140 ns at 35.0 degrees C), thereby suggesting that the conformational relaxation encounters only a small free energy barrier or even proceeds in a downhill manner. Further Langevin dynamics simulations suggest that the observed T-jump relaxation kinetics could be modeled by a conformational diffusion process along a single-well free energy profile, which allowed us to determine the effective diffusion constant and also the roughness of the folding energy landscape.
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Affiliation(s)
- Yao Xu
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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18
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Dumont C, Matsumura Y, Kim SJ, Li J, Kondrashkina E, Kihara H, Gruebele M. Solvent-tuning the collapse and helix formation time scales of lambda(6-85)*. Protein Sci 2007; 15:2596-604. [PMID: 17075136 PMCID: PMC2242409 DOI: 10.1110/ps.062257406] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The lambda(6-85)(*) pseudo-wild type of lambda repressor fragment is a fast two-state folder (k(f) approximately 35 microsec(-1) at 58 degrees C). Previously, highly stable lambda(6-85)(*) mutants with k(f) > 30 microsec(-1) have been engineered to fold nearly or fully downhill. Stabilization of the native state by solvent tuning might also tune lambda(6-85)(*) away from two-state folding. We test this prediction by examining the folding thermodynamics and kinetics of lambda(6-85)(*) in a stabilizing solvent, 45% by weight aqueous ethylene glycol at -28 degrees C. Detection of kinetics by circular dichroism at 222 nm (sensitive to helix content) and small angle X-ray scattering (measuring the radius of gyration) shows that refolding from guanidine hydrochloride denatured conditions exhibits very different time scales for collapse and secondary structure formation: the two processes become decoupled. Collapse remains a low-barrier activated process, while the fastest of several secondary structure formation time scales approaches the downhill folding limit. Two-state folding of lambda(6-85)(*) is not a robust process.
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Affiliation(s)
- Charles Dumont
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Kimura T, Lee JC, Gray HB, Winkler JR. Site-specific collapse dynamics guide the formation of the cytochrome c' four-helix bundle. Proc Natl Acad Sci U S A 2006; 104:117-22. [PMID: 17179212 PMCID: PMC1765420 DOI: 10.1073/pnas.0609413103] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The evolution of tryptophan-to-heme (W/heme) distance distributions extracted from analysis of fluorescence energy transfer kinetics during the refolding of Rhodopseudomonas palustris cytochrome c' reveals dramatic differences between two variants [W32 (Q1A/F32W/W72F) and W72 (Q1A)]. Both W32/heme and W72/heme distance distributions measured at the earliest time point attainable with a continuous-flow mixer (150 mus) confirm that the polypeptide ensemble is not uniformly collapsed and that native structure is not formed. Time-resolved fluorescence spectra indicate that W32 is sequestered from the aqueous solution during the first 700 mus of folding, whereas W72 remains exposed to solvent. The first moment of the W32/heme distance distribution evolves to its native value faster than that of W72, suggesting that the approach of W32 to the heme precedes that of W72.
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Affiliation(s)
- Tetsunari Kimura
- Beckman Institute, California Institute of Technology, Pasadena, CA 91125-7400
| | - Jennifer C. Lee
- Beckman Institute, California Institute of Technology, Pasadena, CA 91125-7400
| | - Harry B. Gray
- Beckman Institute, California Institute of Technology, Pasadena, CA 91125-7400
- To whom correspondence may be addressed. E-mail:
or
| | - Jay R. Winkler
- Beckman Institute, California Institute of Technology, Pasadena, CA 91125-7400
- To whom correspondence may be addressed. E-mail:
or
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Norcross TS, Yeates TO. A framework for describing topological frustration in models of protein folding. J Mol Biol 2006; 362:605-21. [PMID: 16930616 DOI: 10.1016/j.jmb.2006.07.054] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2006] [Revised: 07/19/2006] [Accepted: 07/20/2006] [Indexed: 11/18/2022]
Abstract
In a natively folded protein of moderate or larger size, the protein backbone may weave through itself in complex ways, raising questions about what sequence of events might have to occur in order for the protein to reach its native configuration from the unfolded state. A mathematical framework is presented here for describing the notion of a topological folding barrier, which occurs when a protein chain must pass through a hole or opening, formed by other regions of the protein structure. Different folding pathways encounter different numbers of such barriers and therefore different degrees of frustration. A dynamic programming algorithm finds the optimal theoretical folding path and minimal degree of frustration for a protein based on its natively folded configuration. Calculations over a database of protein structures provide insights into questions such as whether the path of minimal frustration might tend to favor folding from one or from many sites of folding nucleation, or whether proteins favor folding around the N terminus, thereby providing support for the hypothesis that proteins fold co-translationally. The computational methods are applied to a multi-disulfide bonded protein, with computational findings that are consistent with the experimentally observed folding pathway. Attention is drawn to certain complex protein folds for which the computational method suggests there may be a preferred site of nucleation or where folding is likely to proceed through a relatively well-defined pathway or intermediate. The computational analyses lead to testable models for protein folding.
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Affiliation(s)
- Todd S Norcross
- UCLA Department of Chemistry and Biochemistry, UCLA DOE Institute for Genomics and Proteomics, Los Angeles, CA 90095-1569, USA
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