1
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Thakuria S, Paul S. Salt-bridge mediated conformational dynamics in the figure-of-eight knotted ketol acid reductoisomerase (KARI). Phys Chem Chem Phys 2024; 26:24963-24974. [PMID: 39297222 DOI: 10.1039/d4cp02677b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/03/2024]
Abstract
The utility of knotted proteins in biological activities has been ambiguous since their discovery. From their evolutionary significance to their functionality in stabilizing the native protein structure, a unilateral conclusion hasn't been achieved yet. While most studies have been performed to understand the stabilizing effect of the knotted fold on the protein chain, more ideas are yet to emerge regarding the interactions in stabilizing the knot. Using classical molecular dynamics (MD) simulations, we have explored the dynamics of the figure-of-eight knotted domain present in ketol acid reductoisomerase (KARI). Our main focus was on the presence of a salt bridge network evident within the knotted region and its role in shaping the conformational dynamics of the knotted chain. Through the potential of mean forces (PMFs) calculation, we have also marked the specific salt bridges that are pivotal in stabilizing the knotted structure. The correlated motions have been further monitored with the help of principal component analysis (PCA) and dynamic cross-correlation maps (DCCM). Furthermore, mutation of the specific salt bridges led to a change in their conformational stability, vindicating their importance.
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Affiliation(s)
- Sanjib Thakuria
- Department of Chemistry, Indian Institute of Technology, Guwahati, Assam, 781039, India.
| | - Sandip Paul
- Department of Chemistry, Indian Institute of Technology, Guwahati, Assam, 781039, India.
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2
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Zhang M, Nixon R, Schaufelberger F, Pirvu L, De Bo G, Leigh DA. Mechanical scission of a knotted polymer. Nat Chem 2024; 16:1366-1372. [PMID: 38649468 PMCID: PMC11321991 DOI: 10.1038/s41557-024-01510-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Accepted: 03/18/2024] [Indexed: 04/25/2024]
Abstract
Molecular knots and entanglements form randomly and spontaneously in both biological and synthetic polymer chains. It is known that macroscopic materials, such as ropes, are substantially weakened by the presence of knots, but until now it has been unclear whether similar behaviour occurs on a molecular level. Here we show that the presence of a well-defined overhand knot in a polymer chain substantially increases the rate of scission of the polymer under tension (≥2.6× faster) in solution, because deformation of the polymer backbone induced by the tightening knot activates otherwise unreactive covalent bonds. The fragments formed upon severing of the knotted chain differ from those that arise from cleavage of a similar, but unknotted, polymer. Our solution studies provide experimental evidence that knotting can contribute to higher mechanical scission rates of polymers. It also demonstrates that entanglement design can be used to generate mechanophores that are among the most reactive described to date, providing opportunities to increase the reactivity of otherwise inert functional groups.
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Affiliation(s)
- Min Zhang
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, China
- Department of Chemistry, University of Manchester, Manchester, UK
| | - Robert Nixon
- Department of Chemistry, University of Manchester, Manchester, UK
| | | | - Lucian Pirvu
- Department of Chemistry, University of Manchester, Manchester, UK
| | - Guillaume De Bo
- Department of Chemistry, University of Manchester, Manchester, UK.
| | - David A Leigh
- School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, China.
- Department of Chemistry, University of Manchester, Manchester, UK.
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3
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Hsu MF, Sriramoju MK, Lai CH, Chen YR, Huang JS, Ko TP, Huang KF, Hsu STD. Structure, dynamics, and stability of the smallest and most complex 7 1 protein knot. J Biol Chem 2024; 300:105553. [PMID: 38072060 PMCID: PMC10840475 DOI: 10.1016/j.jbc.2023.105553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 11/21/2023] [Accepted: 12/04/2023] [Indexed: 12/29/2023] Open
Abstract
Proteins can spontaneously tie a variety of intricate topological knots through twisting and threading of the polypeptide chains. Recently developed artificial intelligence algorithms have predicted several new classes of topological knotted proteins, but the predictions remain to be authenticated experimentally. Here, we showed by X-ray crystallography and solution-state NMR spectroscopy that Q9PR55, an 89-residue protein from Ureaplasma urealyticum, possesses a novel 71 knotted topology that is accurately predicted by AlphaFold 2, except for the flexible N terminus. Q9PR55 is monomeric in solution, making it the smallest and most complex knotted protein known to date. In addition to its exceptional chemical stability against urea-induced unfolding, Q9PR55 is remarkably robust to resist the mechanical unfolding-coupled proteolysis by a bacterial proteasome, ClpXP. Our results suggest that the mechanical resistance against pulling-induced unfolding is determined by the complexity of the knotted topology rather than the size of the molecule.
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Affiliation(s)
- Min-Feng Hsu
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | | | - Chih-Hsuan Lai
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Yun-Ru Chen
- Academia Sinica Protein Clinic, Academia Sinica, Taipei, Taiwan
| | - Jing-Siou Huang
- Academia Sinica Protein Clinic, Academia Sinica, Taipei, Taiwan
| | - Tzu-Ping Ko
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Kai-Fa Huang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Academia Sinica Protein Clinic, Academia Sinica, Taipei, Taiwan
| | - Shang-Te Danny Hsu
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Academia Sinica Protein Clinic, Academia Sinica, Taipei, Taiwan; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan; International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM(2)), Hiroshima University, Higashihiroshima, Japan.
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4
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Hsu STD. Folding and functions of knotted proteins. Curr Opin Struct Biol 2023; 83:102709. [PMID: 37778185 DOI: 10.1016/j.sbi.2023.102709] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Revised: 09/02/2023] [Accepted: 09/05/2023] [Indexed: 10/03/2023]
Abstract
Topologically knotted proteins have entangled structural elements within their native structures that cannot be disentangled simply by pulling from the N- and C-termini. Systematic surveys have identified different types of knotted protein structures, constituting as much as 1% of the total entries within the Protein Data Bank. Many knotted proteins rely on their knotted structural elements to carry out evolutionarily conserved biological functions. Being knotted may also provide mechanical stability to withstand unfolding-coupled proteolysis. Reconfiguring a knotted protein topology by circular permutation or cyclization provides insights into the importance of being knotted in the context of folding and functions. With the explosion of predicted protein structures by artificial intelligence, we are now entering a new era of exploring the entangled protein universe.
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Affiliation(s)
- Shang-Te Danny Hsu
- Institute of Biological Chemistry, Academia Sinica, Taipei 11529, Taiwan; Institute of Biochemical Sciences, National Taiwan University, Taipei 10617, Taiwan; International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM(2)), Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
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5
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Doyle LA, Takushi B, Kibler RD, Milles LF, Orozco CT, Jones JD, Jackson SE, Stoddard BL, Bradley P. De novo design of knotted tandem repeat proteins. Nat Commun 2023; 14:6746. [PMID: 37875492 PMCID: PMC10598012 DOI: 10.1038/s41467-023-42388-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Accepted: 10/09/2023] [Indexed: 10/26/2023] Open
Abstract
De novo protein design methods can create proteins with folds not yet seen in nature. These methods largely focus on optimizing the compatibility between the designed sequence and the intended conformation, without explicit consideration of protein folding pathways. Deeply knotted proteins, whose topologies may introduce substantial barriers to folding, thus represent an interesting test case for protein design. Here we report our attempts to design proteins with trefoil (31) and pentafoil (51) knotted topologies. We extended previously described algorithms for tandem repeat protein design in order to construct deeply knotted backbones and matching designed repeat sequences (N = 3 repeats for the trefoil and N = 5 for the pentafoil). We confirmed the intended conformation for the trefoil design by X ray crystallography, and we report here on this protein's structure, stability, and folding behaviour. The pentafoil design misfolded into an asymmetric structure (despite a 5-fold symmetric sequence); two of the four repeat-repeat units matched the designed backbone while the other two diverged to form local contacts, leading to a trefoil rather than pentafoil knotted topology. Our results also provide insights into the folding of knotted proteins.
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Affiliation(s)
- Lindsey A Doyle
- Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. North, Seattle, WA, 98109, USA
| | - Brittany Takushi
- Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. North, Seattle, WA, 98109, USA
| | - Ryan D Kibler
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA
| | - Lukas F Milles
- Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA
| | - Carolina T Orozco
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Jonathan D Jones
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Sophie E Jackson
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Barry L Stoddard
- Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. North, Seattle, WA, 98109, USA.
| | - Philip Bradley
- Division of Basic Sciences, Fred Hutchinson Cancer Center, 1100 Fairview Ave. North, Seattle, WA, 98109, USA.
- Division of Public Health Sciences and Program in Computational Biology, Fred Hutchinson Cancer Center, 1100 Fairview Ave. N, Seattle, WA, 98009, USA.
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6
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7
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Capała K, Szymczak P. Stochastic model of translocation of knotted proteins. Phys Rev E 2022; 106:054406. [PMID: 36559434 DOI: 10.1103/physreve.106.054406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 10/25/2022] [Indexed: 11/16/2022]
Abstract
Knotted proteins, when forced through the pores, can get stuck if the knots in their backbone tighten under force. Alternatively, the knot can slide off the chain, making translocation possible. We construct a simple energy landscape model of this process with a time-periodic potential that mimics the action of a molecular motor. We calculate the translocation time as a function of the period of the pulling force, discuss the asymptotic limits and biological relevance of the results.
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Affiliation(s)
- Karol Capała
- Personal Health Data Science Group, Sano - Centre for Computational Personalised Medicine, Czarnowiejska 36, 30-054 Kraków, Poland and Institute of Theoretical Physics, Department of Statistical Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland
| | - Piotr Szymczak
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warsaw, Poland
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8
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Xu Y, Kang R, Ren L, Yang L, Yue T. Revealing Topological Barriers against Knot Untying in Thermal and Mechanical Protein Unfolding by Molecular Dynamics Simulations. Biomolecules 2021; 11:1688. [PMID: 34827686 PMCID: PMC8615548 DOI: 10.3390/biom11111688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Revised: 10/20/2021] [Accepted: 10/21/2021] [Indexed: 11/16/2022] Open
Abstract
The knot is one of the most remarkable topological features identified in an increasing number of proteins with important functions. However, little is known about how the knot is formed during protein folding, and untied or maintained in protein unfolding. By means of all-atom molecular dynamics simulation, here we employ methyltransferase YbeA as the knotted protein model to analyze changes of the knotted conformation coupled with protein unfolding under thermal and mechanical denaturing conditions. Our results show that the trefoil knot in YbeA is occasionally untied via knot loosening rather than sliding under enhanced thermal fluctuations. Through correlating protein unfolding with changes in the knot position and size, several aspects of barriers that jointly suppress knot untying are revealed. In particular, protein unfolding is always prior to knot untying and starts preferentially from separation of two α-helices (α1 and α5), which protect the hydrophobic core consisting of β-sheets (β1-β4) from exposure to water. These β-sheets form a loop through which α5 is threaded to form the knot. Hydrophobic and hydrogen bonding interactions inside the core stabilize the loop against loosening. In addition, residues at N-terminal of α5 define a rigid turning to impede α5 from sliding out of the loop. Site mutations are designed to specifically eliminate these barriers, and easier knot untying is achieved under the same denaturing conditions. These results provide new molecular level insights into the folding/unfolding of knotted proteins.
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Affiliation(s)
- Yan Xu
- College of Electronic Engineering and Automation, Shandong University of Science and Technology, Qingdao 266590, China;
- College of Chemical Engineering, China University of Petroleum (East China), Qingdao 266580, China;
| | - Runshan Kang
- College of Chemical Engineering, China University of Petroleum (East China), Qingdao 266580, China;
| | - Luyao Ren
- Key Laboratory of Marine Environment and Ecology, Institute of Coastal Environmental Pollution Control, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; (L.R.); (L.Y.)
| | - Lin Yang
- Key Laboratory of Marine Environment and Ecology, Institute of Coastal Environmental Pollution Control, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; (L.R.); (L.Y.)
| | - Tongtao Yue
- Key Laboratory of Marine Environment and Ecology, Institute of Coastal Environmental Pollution Control, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; (L.R.); (L.Y.)
- Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China
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9
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Fonseka HYY, Javidi A, Oliveira LFL, Micheletti C, Stan G. Unfolding and Translocation of Knotted Proteins by Clp Biological Nanomachines: Synergistic Contribution of Primary Sequence and Topology Revealed by Molecular Dynamics Simulations. J Phys Chem B 2021; 125:7335-7350. [PMID: 34110163 DOI: 10.1021/acs.jpcb.1c00898] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We use Langevin dynamics simulations to model, at an atomistic resolution, how various natively knotted proteins are unfolded in repeated allosteric translocating cycles of the ClpY ATPase. We consider proteins representative of different topologies, from the simplest knot (trefoil 31), to the three-twist 52 knot, to the most complex stevedore, 61, knot. We harness the atomistic detail of the simulations to address aspects that have so far remained largely unexplored, such as sequence-dependent effects on the ruggedness of the landscape traversed during knot sliding. Our simulations reveal the combined effect on translocation of the knotted protein structure, i.e., backbone topology and geometry, and primary sequence, i.e., side chain size and interactions, and show that the latter can dominate translocation hindrance. In addition, we observe that due to the interplay between the knotted topology and intramolecular contacts the transmission of tension along the polypeptide chain occurs very differently from that of homopolymers. Finally, by considering native and non-native interactions, we examine how the disruption or formation of such contacts can affect the translocation processivity and concomitantly create multiple unfolding pathways with very different activation barriers.
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Affiliation(s)
| | - Alex Javidi
- Data Sciences, Janssen Research and Development, Spring House, Pennsylvania 19477, United States
| | - Luiz F L Oliveira
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States
| | - Cristian Micheletti
- Molecular and Statistical Biophysics, Scuola Internazionale Superiore di Studi Avanzati (SISSA), 34136 Trieste, Italy
| | - George Stan
- Department of Chemistry, University of Cincinnati, Cincinnati, Ohio 45221, United States
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10
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Paissoni C, Puri S, Wang I, Chen SY, Camilloni C, Hsu STD. Converging experimental and computational views of the knotting mechanism of a small knotted protein. Biophys J 2021; 120:2276-2286. [PMID: 33812848 PMCID: PMC8390826 DOI: 10.1016/j.bpj.2021.03.032] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 02/14/2021] [Accepted: 03/29/2021] [Indexed: 01/18/2023] Open
Abstract
MJ0366 from Methanocaldococcus jannaschii is the smallest topologically knotted protein known to date. 92 residues in length, MJ0366 ties a trefoil (31) knot by threading its C-terminal helix through a buttonhole formed by the remainder of the secondary structure elements. By generating a library of point mutations at positions pertinent to the knot formation, we systematically evaluated the contributions of individual residues to the folding stability and kinetics of MJ0366. The experimental Φ-values were used as restraints to computationally generate an ensemble of conformations that correspond to the transition state of MJ0366, which revealed several nonnative contacts. The importance of these nonnative contacts in stabilizing the transition state of MJ0366 was confirmed by a second round of mutagenesis, which also established the pivotal role of F15 in stapling the network of hydrophobic interactions around the threading C-terminal helix. Our converging experimental and computational results show that, despite the small size, the transition state of MJ0366 is formed at a very late stage of the folding reaction coordinate, following a polarized pathway. Eventually, the formation of extensive native contacts, as well as a number of nonnative ones, leads to the threading of the C-terminal helix that defines the topological knot.
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Affiliation(s)
- Cristina Paissoni
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milano, Italy
| | - Sarita Puri
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Iren Wang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Szu-Yu Chen
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
| | - Carlo Camilloni
- Dipartimento di Bioscienze, Università degli Studi di Milano, Milano, Italy.
| | - Shang-Te Danny Hsu
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan; Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.
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11
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Wang H, Li H. Mechanically tightening, untying and retying a protein trefoil knot by single-molecule force spectroscopy. Chem Sci 2020; 11:12512-12521. [PMID: 34123232 PMCID: PMC8162576 DOI: 10.1039/d0sc02796k] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Knotted conformation is one of the most surprising topological features found in proteins, and understanding the folding mechanism of such knotted proteins remains a challenge. Here, we used optical tweezers (OT) to investigate the mechanical unfolding and folding behavior of a knotted protein Escherichia coli tRNA (guanosine-1) methyltransferase (TrmD). We found that when stretched from its N- and C-termini, TrmD can be mechanically unfolded and stretched into a tightened trefoil knot, which is composed of ca. 17 residues. Stretching of the unfolded TrmD involved a compaction process of the trefoil knot at low forces. The unfolding pathways of the TrmD were bifurcated, involving two-state and three-state pathways. Upon relaxation, the tightened trefoil knot loosened up first, leading to the expansion of the knot, and the unfolded TrmD can then fold back to its native state efficiently. By using an engineered truncation TrmD variant, we stretched TrmD along a pulling direction to allow us to mechanically unfold TrmD and untie the trefoil knot. We found that the folding of TrmD from its unfolded polypeptide without the knot is significantly slower. The knotting is the rate-limiting step of the folding of TrmD. Our results highlighted the critical importance of the knot conformation for the folding and stability of TrmD, offering a new perspective to understand the role of the trefoil knot in the biological function of TrmD. Optical tweezers are used to stretch a knotted protein along different directions to probe its unfolding–folding behaviors, and the conformational change of its knot structure. ![]()
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Affiliation(s)
- Han Wang
- Department of Chemistry, University of British Columbia Vancouver BC V6T 1Z1 Canada
| | - Hongbin Li
- Department of Chemistry, University of British Columbia Vancouver BC V6T 1Z1 Canada
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12
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Smalyukh II. Review: knots and other new topological effects in liquid crystals and colloids. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2020; 83:106601. [PMID: 32721944 DOI: 10.1088/1361-6633/abaa39] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Humankind has been obsessed with knots in religion, culture and daily life for millennia, while physicists like Gauss, Kelvin and Maxwell already involved them in models centuries ago. Nowadays, colloidal particles can be fabricated to have shapes of knots and links with arbitrary complexity. In liquid crystals, closed loops of singular vortex lines can be knotted by using colloidal particles and laser tweezers, as well as by confining nematic fluids into micrometer-sized droplets with complex topology. Knotted and linked colloidal particles induce knots and links of singular defects, which can be interlinked (or not) with colloidal particle knots, revealing the diversity of interactions between topologies of knotted fields and topologically nontrivial surfaces of colloidal objects. Even more diverse knotted structures emerge in nonsingular molecular alignment and magnetization fields in liquid crystals and colloidal ferromagnets. The topological solitons include hopfions, skyrmions, heliknotons, torons and other spatially localized continuous structures, which are classified based on homotopy theory, characterized by integer-valued topological invariants and often contain knotted or linked preimages, nonsingular regions of space corresponding to single points of the order parameter space. A zoo of topological solitons in liquid crystals, colloids and ferromagnets promises new breeds of information displays and a plethora of data storage, electro-optic and photonic applications. Their particle-like collective dynamics echoes coherent motions in active matter, ranging from crowds of people to schools of fish. This review discusses the state of the art in the field, as well as highlights recent developments and open questions in physics of knotted soft matter. We systematically overview knotted field configurations, the allowed transformations between them, their physical stability and how one can use one form of knotted fields to model, create and imprint other forms. The large variety of symmetries accessible to liquid crystals and colloids offer insights into stability, transformation and emergent dynamics of fully nonsingular and singular knotted fields of fundamental and applied importance. The common thread of this review is the ability to experimentally visualize these knots in real space. The review concludes with a discussion of how the studies of knots in liquid crystals and colloids can offer insights into topologically related structures in other branches of physics, with answers to many open questions, as well as how these experimentally observable knots hold a strong potential for providing new inspirations to the mathematical knot theory.
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Affiliation(s)
- Ivan I Smalyukh
- Department of Physics, Department of Electrical, Computer and Energy Engineering, Materials Science and Engineering Program and Soft Materials Research Center, University of Colorado, Boulder, CO 80309, United States of America
- Renewable and Sustainable Energy Institute, National Renewable Energy Laboratory and University of Colorado, Boulder, CO 80309, United States of America
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13
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Piejko M, Niewieczerzal S, Sulkowska JI. The Folding of Knotted Proteins: Distinguishing the Distinct Behavior of Shallow and Deep Knots. Isr J Chem 2020. [DOI: 10.1002/ijch.202000036] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Maciej Piejko
- Faculty of ChemistryUniversity of Warsaw Pasteura 1 Warsaw 02-093 Poland
- Centre of New TechnologiesUniversity of Warsaw Banacha 2c Warsaw 02-097 Poland
| | | | - Joanna I. Sulkowska
- Faculty of ChemistryUniversity of Warsaw Pasteura 1 Warsaw 02-093 Poland
- Centre of New TechnologiesUniversity of Warsaw Banacha 2c Warsaw 02-097 Poland
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14
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Transient knots in intrinsically disordered proteins and neurodegeneration. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2020; 174:79-103. [PMID: 32828471 DOI: 10.1016/bs.pmbts.2020.03.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We provide a brief overview of the topological features found in structured proteins and of the dynamical processes that involve knots. We then discuss the knotted states that arise in the intrinsically disordered polyglutamine and α-synuclein. We argue that the existence of the knotted conformations stalls degradation by proteases and thus enhances aggregation. This mechanism works if the length of a peptide chain exceeds a threshold, as in the Huntington disease. We also study the cavities that form within the conformations of the disordered proteins. The volume of the cavities varies in time in a way that is different than that of the radius of gyration or the end-to-end distance. In addition, we study the traffic between the conformational basins and identify patterns associated with the deep and shallow knots. The results are obtained by molecular dynamics simulations that use coarse-grained and all-atom models (with and without the explicit solvent).
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15
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Chwastyk M, Cieplak M. Conformational Biases of α-Synuclein and Formation of Transient Knots. J Phys Chem B 2019; 124:11-19. [DOI: 10.1021/acs.jpcb.9b08481] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Mateusz Chwastyk
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | - Marek Cieplak
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
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16
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Perego C, Potestio R. Computational methods in the study of self-entangled proteins: a critical appraisal. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:443001. [PMID: 31269476 DOI: 10.1088/1361-648x/ab2f19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The existence of self-entangled proteins, the native structure of which features a complex topology, unveils puzzling, and thus fascinating, aspects of protein biology and evolution. The discovery that a polypeptide chain can encode the capability to self-entangle in an efficient and reproducible way during folding, has raised many questions, regarding the possible function of these knots, their conservation along evolution, and their role in the folding paradigm. Understanding the function and origin of these entanglements would lead to deep implications in protein science, and this has stimulated the scientific community to investigate self-entangled proteins for decades by now. In this endeavour, advanced experimental techniques are more and more supported by computational approaches, that can provide theoretical guidelines for the interpretation of experimental results, and for the effective design of new experiments. In this review we provide an introduction to the computational study of self-entangled proteins, focusing in particular on the methodological developments related to this research field. A comprehensive collection of techniques is gathered, ranging from knot theory algorithms, that allow detection and classification of protein topology, to Monte Carlo or molecular dynamics strategies, that constitute crucial instruments for investigating thermodynamics and kinetics of this class of proteins.
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Affiliation(s)
- Claudio Perego
- Max Panck Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany
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17
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Xu Y, Li S, Yan Z, Ge B, Huang F, Yue T. Revealing Cooperation between Knotted Conformation and Dimerization in Protein Stabilization by Molecular Dynamics Simulations. J Phys Chem Lett 2019; 10:5815-5822. [PMID: 31525988 DOI: 10.1021/acs.jpclett.9b02209] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The topological knot is thought to play a stabilizing role in maintaining the global fold and nature of proteins with the underlying mechanism yet to be elucidated. Given that most proteins containing trefoil knots exist and function as homodimers with a large part of the dimer interface occupied by the knotted region, we reason that the knotted conformation cooperates with dimerization in protein stabilization. Here, we take YbeA from Escherichia coli as the knotted protein model, using molecular dynamics (MD) simulations to compare the stability of two pairs of dimeric proteins having the same sequence and secondary structures but differing in the presence or absence of a trefoil knot in each subunit. The dimer interface of YbeA is identified to involve favorable contacts among three α-helices (α1, α3, and α5), one of which (α5) is threaded through a loop connected with α3 to form the knot. Upon removal of the knot by appropriate change of the knot-making crossing of the polypeptide chain, relevant domains are less constrained and exhibit enhanced fluctuations to decrease contacts at the interface. Unknotted subunits are less compact and undergo structural changes to ease the dimer separation. Such a stabilizing effect is evidenced by steered MD simulations, showing that the mechanical force required for dimer separation is significantly reduced by removing the knot. In addition to the knotted conformation, dimerization further improves the protein stability by restricting the α1-α5 separation, which is defined as a leading step for protein unfolding. These results provide important insights into the structure-function relationship of dimerization in knotted proteins.
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Affiliation(s)
- Yan Xu
- State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, College of Chemical Engineering , China University of Petroleum (East China) , Qingdao 266580 , China
- College of Electronic Engineering and Automation , Shandong University of Science and Technology , Qingdao 266590 , China
| | - Shixin Li
- State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, College of Chemical Engineering , China University of Petroleum (East China) , Qingdao 266580 , China
| | - Zengshuai Yan
- State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, College of Chemical Engineering , China University of Petroleum (East China) , Qingdao 266580 , China
| | - Baosheng Ge
- State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, College of Chemical Engineering , China University of Petroleum (East China) , Qingdao 266580 , China
| | - Fang Huang
- State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, College of Chemical Engineering , China University of Petroleum (East China) , Qingdao 266580 , China
| | - Tongtao Yue
- State Key Laboratory of Heavy Oil Processing, Center for Bioengineering and Biotechnology, College of Chemical Engineering , China University of Petroleum (East China) , Qingdao 266580 , China
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18
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Wang H, Gao X, Hu X, Hu X, Hu C, Li H. Mechanical Unfolding and Folding of a Complex Slipknot Protein Probed by Using Optical Tweezers. Biochemistry 2019; 58:4751-4760. [DOI: 10.1021/acs.biochem.9b00320] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Han Wang
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Xiaoqing Gao
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- State Key Laboratory of Precision Measurements Technology Instruments, School of Precision Instrument Optoelectronics Engineering, Tianjin University, Tianjin 300072, People’s Republic of China
| | - Xiaodong Hu
- State Key Laboratory of Precision Measurements Technology Instruments, School of Precision Instrument Optoelectronics Engineering, Tianjin University, Tianjin 300072, People’s Republic of China
| | - Xiaotang Hu
- State Key Laboratory of Precision Measurements Technology Instruments, School of Precision Instrument Optoelectronics Engineering, Tianjin University, Tianjin 300072, People’s Republic of China
| | - Chunguang Hu
- State Key Laboratory of Precision Measurements Technology Instruments, School of Precision Instrument Optoelectronics Engineering, Tianjin University, Tianjin 300072, People’s Republic of China
| | - Hongbin Li
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- State Key Laboratory of Precision Measurements Technology Instruments, School of Precision Instrument Optoelectronics Engineering, Tianjin University, Tianjin 300072, People’s Republic of China
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19
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He C, Li S, Gao X, Xiao A, Hu C, Hu X, Hu X, Li H. Direct observation of the fast and robust folding of a slipknotted protein by optical tweezers. NANOSCALE 2019; 11:3945-3951. [PMID: 30762052 DOI: 10.1039/c8nr10070e] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Understanding the folding mechanism of knotted and slipknotted proteins has attracted considerable interest. Due to their topological complexity, knotted and slipknotted proteins are predicted to fold slowly and involve large topological barriers. Molecular dynamics simulation studies suggest that a slipknotted conformation can serve as an important intermediate to help greatly reduce the topological difficulty during the folding of some knotted proteins. Here we use a single molecule optical tweezers technique to directly probe the folding of a small slipknotted protein AFV3-109. We found that stretching AFV3-109 can lead to the untying of the slipknot and complete unfolding of AFV3-109. Upon relaxation, AFV3-109 can readily refold back to its native slipknot conformation with high fidelity when the stretching force is lower than 6 pN. The refolding of AFV3-109 occurs in a sharp two-state like transition. Our results indicate that, different from knotted proteins, the folding of a slipknotted protein like AFV3-109 can be fast, and may not necessarily involve a high topological barrier.
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Affiliation(s)
- Chengzhi He
- State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, P. R. China. and Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Shuai Li
- State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, P. R. China. and Nanchang Institute for Microtechnology of Tianjin University, Tianjin, 300072, P.R. China
| | - Xiaoqing Gao
- State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, P. R. China. and Nanchang Institute for Microtechnology of Tianjin University, Tianjin, 300072, P.R. China
| | - Adam Xiao
- Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Chunguang Hu
- State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, P. R. China. and Nanchang Institute for Microtechnology of Tianjin University, Tianjin, 300072, P.R. China
| | - Xiaodong Hu
- State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, P. R. China. and Nanchang Institute for Microtechnology of Tianjin University, Tianjin, 300072, P.R. China
| | - Xiaotang Hu
- State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, P. R. China. and Nanchang Institute for Microtechnology of Tianjin University, Tianjin, 300072, P.R. China
| | - Hongbin Li
- State Key Laboratory of Precision Measuring Technology and Instruments, School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, 300072, P. R. China. and Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
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20
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Sivertsson EM, Jackson SE, Itzhaki LS. The AAA+ protease ClpXP can easily degrade a 3 1 and a 5 2-knotted protein. Sci Rep 2019; 9:2421. [PMID: 30787316 PMCID: PMC6382783 DOI: 10.1038/s41598-018-38173-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2018] [Accepted: 12/04/2018] [Indexed: 12/16/2022] Open
Abstract
Knots in proteins are hypothesized to make them resistant to enzymatic degradation by ATP-dependent proteases and recent studies have shown that whereas ClpXP can easily degrade a protein with a shallow 31 knot, it cannot degrade 52-knotted proteins if degradation is initiated at the C-terminus. Here, we present detailed studies of the degradation of both 31- and 52-knotted proteins by ClpXP using numerous constructs where proteins are tagged for degradation at both N- and C-termini. Our results confirm and extend earlier work and show that ClpXP can easily degrade a deeply 31-knotted protein. In contrast to recently published work on the degradation of 52-knotted proteins, our results show that the ClpXP machinery can also easily degrade these proteins. However, the degradation depends critically on the location of the degradation tag and the local stability near the tag. Our results are consistent with mechanisms in which either the knot simply slips along the polypeptide chain and falls off the free terminus, or one in which the tightened knot enters the translocation pore of ClpXP. Results of experiments on knotted protein fusions with a highly stable domain show partial degradation and the formation of degradation intermediates.
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Affiliation(s)
- Elin M Sivertsson
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1PD, UK
| | - Sophie E Jackson
- Department of Chemistry, Lensfield Road, Cambridge, CB2 1EW, UK.
| | - Laura S Itzhaki
- Department of Pharmacology, Tennis Court Road, Cambridge, CB2 1PD, UK.
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21
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Xu Y, Li S, Yan Z, Luo Z, Ren H, Ge B, Huang F, Yue T. Stabilizing Effect of Inherent Knots on Proteins Revealed by Molecular Dynamics Simulations. Biophys J 2018; 115:1681-1689. [PMID: 30314655 PMCID: PMC6225051 DOI: 10.1016/j.bpj.2018.09.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 09/11/2018] [Accepted: 09/18/2018] [Indexed: 10/28/2022] Open
Abstract
A growing number of proteins have been identified as knotted in their native structures, with such entangled topological features being expected to play stabilizing roles maintaining both the global fold and the nature of proteins. However, the molecular mechanism underlying the stabilizing effect is ambiguous. Here, we combine unbiased and mechanical atomistic molecular dynamics simulations to investigate how a protein is stabilized by an inherent knot by directly comparing chemical, thermal, and mechanical denaturing properties of two proteins having the same sequence and secondary structures but differing in the presence or absence of an inherent knot. One protein is YbeA from Escherichia coli, containing a deep trefoil knot within the sequence, and the other is the modified protein with the knot of YbeA being removed. Under certain chemical denaturing conditions, the unknotted protein fully unfolds whereas the knotted protein does not, suggesting a higher intrinsic stability for the protein having a knot. Both proteins unfold under enhanced thermal fluctuations but at different rates and with distinct pathways. Opening the hydrophobic core via separation between two α-helices is identified as a crucial step initiating the protein unfolding, which, however, is restrained for the knotted protein by topological and geometrical frustrations. Energy barriers for denaturing the protein are reduced by removing the knot, as evidenced by mechanical unfolding simulations. Finally, yet importantly, no obvious change in size or location of the knot was observed during denaturing processes, indicating that YbeA may remain knotted for a relatively long time during and after denaturation.
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Affiliation(s)
- Yan Xu
- State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum (East China), Qingdao, China
| | - Shixin Li
- Center for Bioengineering and Biotechnology, College of Chemical Engineering, China University of Petroleum (East China), Qingdao, China
| | - Zengshuai Yan
- Center for Bioengineering and Biotechnology, College of Chemical Engineering, China University of Petroleum (East China), Qingdao, China
| | - Zhen Luo
- Center for Bioengineering and Biotechnology, College of Chemical Engineering, China University of Petroleum (East China), Qingdao, China
| | - Hao Ren
- Center for Bioengineering and Biotechnology, College of Chemical Engineering, China University of Petroleum (East China), Qingdao, China
| | - Baosheng Ge
- Center for Bioengineering and Biotechnology, College of Chemical Engineering, China University of Petroleum (East China), Qingdao, China
| | - Fang Huang
- State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum (East China), Qingdao, China
| | - Tongtao Yue
- State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering, China University of Petroleum (East China), Qingdao, China; Center for Bioengineering and Biotechnology, College of Chemical Engineering, China University of Petroleum (East China), Qingdao, China.
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22
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Jarmolinska AI, Perlinska AP, Runkel R, Trefz B, Ginn HM, Virnau P, Sulkowska JI. Proteins' Knotty Problems. J Mol Biol 2018; 431:244-257. [PMID: 30391297 DOI: 10.1016/j.jmb.2018.10.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Revised: 10/17/2018] [Accepted: 10/17/2018] [Indexed: 12/20/2022]
Abstract
Knots in proteins are increasingly being recognized as an important structural concept, and the folding of these peculiar structures still poses considerable challenges. From a functional point of view, most protein knots discovered so far are either enzymes or DNA-binding proteins. Our comprehensive topological analysis of the Protein Data Bank reveals several novel structures including knotted mitochondrial proteins and the most deeply embedded protein knot discovered so far. For the latter, we propose a novel folding pathway based on the idea that a loose knot forms at a terminus and slides to its native position. For the mitochondrial proteins, we discuss the folding problem from the perspective of transport and suggest that they fold inside the mitochondria. We also discuss the evolutionary origin of a novel class of knotted membrane proteins and argue that a novel knotted DNA-binding protein constitutes a new fold. Finally, we have also discovered a knot in an artificially designed protein structure.
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Affiliation(s)
- Aleksandra I Jarmolinska
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland; College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, Banacha 2c, 02-097 Warsaw, Poland
| | - Agata P Perlinska
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland; College of Inter-Faculty Individual Studies in Mathematics and Natural Sciences, Banacha 2c, 02-097 Warsaw, Poland
| | - Robert Runkel
- Department of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Benjamin Trefz
- Department of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany; Graduate School Material Science in Mainz, Staudinger Weg 9, 55128 Mainz, Germany
| | - Helen M Ginn
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Peter Virnau
- Department of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Joanna I Sulkowska
- Centre of New Technologies, University of Warsaw, Banacha 2c, 02-097 Warsaw, Poland.
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23
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Zhao Y, Cieplak M. Stability of structurally entangled protein dimers. Proteins 2018; 86:945-955. [DOI: 10.1002/prot.25526] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/23/2018] [Accepted: 05/14/2018] [Indexed: 12/12/2022]
Affiliation(s)
- Yani Zhao
- Institute of Physics, Polish Academy of Sciences; Aleja Lotników 32/46, Warsaw 02668 Poland
| | - Marek Cieplak
- Institute of Physics, Polish Academy of Sciences; Aleja Lotników 32/46, Warsaw 02668 Poland
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24
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Zhao Y, Chwastyk M, Cieplak M. Structural entanglements in protein complexes. J Chem Phys 2018; 146:225102. [PMID: 29166058 DOI: 10.1063/1.4985221] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
We consider multi-chain protein native structures and propose a criterion that determines whether two chains in the system are entangled or not. The criterion is based on the behavior observed by pulling at both termini of each chain simultaneously in the two chains. We have identified about 900 entangled systems in the Protein Data Bank and provided a more detailed analysis for several of them. We argue that entanglement enhances the thermodynamic stability of the system but it may have other functions: burying the hydrophobic residues at the interface and increasing the DNA or RNA binding area. We also study the folding and stretching properties of the knotted dimeric proteins MJ0366, YibK, and bacteriophytochrome. These proteins have been studied theoretically in their monomeric versions so far. The dimers are seen to separate on stretching through the tensile mechanism and the characteristic unraveling force depends on the pulling direction.
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Affiliation(s)
- Yani Zhao
- Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland
| | - Mateusz Chwastyk
- Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland
| | - Marek Cieplak
- Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland
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25
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Sulkowska JI, Sułkowski P. Entangled Proteins: Knots, Slipknots, Links, and Lassos. SPRINGER SERIES IN SOLID-STATE SCIENCES 2018. [DOI: 10.1007/978-3-319-76596-9_8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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26
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Dabrowski-Tumanski P, Sulkowska JI. To Tie or Not to Tie? That Is the Question. Polymers (Basel) 2017; 9:E454. [PMID: 30965758 PMCID: PMC6418553 DOI: 10.3390/polym9090454] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Revised: 09/11/2017] [Accepted: 09/12/2017] [Indexed: 12/18/2022] Open
Abstract
In this review, we provide an overview of entangled proteins. Around 6% of protein structures deposited in the PBD are entangled, forming knots, slipknots, lassos and links. We present theoretical methods and tools that enabled discovering and classifying such structures. We discuss the advantages and disadvantages of the non-trivial topology in proteins, based on available data about folding, stability, biological properties and evolutionary conservation. We also formulate intriguing and challenging questions on the border of biophysics, bioinformatics, biology and mathematics, which arise from the discovery of an entanglement in proteins. Finally, we discuss possible applications of entangled proteins in medicine and nanotechnology, such as the chance to design super stable proteins, whose stability could be controlled by chemical potential.
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Affiliation(s)
- Pawel Dabrowski-Tumanski
- Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland.
- Faculty of Chemistry, University of Warsaw, Warsaw 02-093, Poland.
| | - Joanna I Sulkowska
- Centre of New Technologies, University of Warsaw, Warsaw 02-097, Poland.
- Faculty of Chemistry, University of Warsaw, Warsaw 02-093, Poland.
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27
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Haglund E, Pilko A, Wollman R, Jennings PA, Onuchic JN. Pierced Lasso Topology Controls Function in Leptin. J Phys Chem B 2017; 121:706-718. [PMID: 28035835 DOI: 10.1021/acs.jpcb.6b11506] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein engineering is a powerful tool in drug design and therapeutics, where disulphide bridges are commonly introduced to stabilize proteins. However, these bonds also introduce covalent loops, which are often neglected. These loops may entrap the protein backbone on opposite sides, leading to a "knotted" topology, forming a so-called Pierced Lasso (PL). In this elegant system, the "knot" is held together with a single disulphide bridge where part of the polypeptide chain is threaded through. The size and position of these covalent loops can be manipulated through protein design in vitro, whereas nature uses polymorphism to switch the PL topology. The PL protein leptin shows genetic modification of an N-terminal residue, adding a third cysteine to the same sequence. In an effort to understand the mechanism of threading of these diverse topologies, we designed three loop variants to mimic the polymorphic sequence. This adds elegance to the system under study, as it allows the generation of three possible covalent loops; they are the original wild-type C-terminal loop protein, the fully circularized unthreaded protein, and the N-terminal loop protein, responsible for different lasso topologies. The size of the loop changes the threading mechanism from a slipknotting to a plugging mechanism, with increasing loop size. Interestingly, the ground state of the native protein structure is largely unaffected, but biological assays show that the activity is maximized by properly controlled dynamics in the threaded state. A threaded topology with proper conformational dynamics is important for receptor interaction and activation of the signaling pathways in vivo.
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Affiliation(s)
- Ellinor Haglund
- Center for Theoretical Biological Physics (CTBP) and Departments of Physics and Astronomy, Chemistry and Biosciences, Rice University , Houston, Texas, United States
| | - Anna Pilko
- Department of Chemistry and Biochemistry, The University of California, San Diego (UCSD) , La Jolla, California, United States
| | - Roy Wollman
- Department of Chemistry and Biochemistry, The University of California, San Diego (UCSD) , La Jolla, California, United States
| | - Patricia Ann Jennings
- Department of Chemistry and Biochemistry, The University of California, San Diego (UCSD) , La Jolla, California, United States
| | - José Nelson Onuchic
- Center for Theoretical Biological Physics (CTBP) and Departments of Physics and Astronomy, Chemistry and Biosciences, Rice University , Houston, Texas, United States
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28
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Jackson SE, Suma A, Micheletti C. How to fold intricately: using theory and experiments to unravel the properties of knotted proteins. Curr Opin Struct Biol 2016; 42:6-14. [PMID: 27794211 DOI: 10.1016/j.sbi.2016.10.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/06/2016] [Accepted: 10/03/2016] [Indexed: 11/15/2022]
Abstract
Over the years, advances in experimental and computational methods have helped us to understand the role of thermodynamic, kinetic and active (chaperone-aided) effects in coordinating the folding steps required to achieving a knotted native state. Here, we review such developments by paying particular attention to the complementarity of experimental and computational studies. Key open issues that could be tackled with either or both approaches are finally pointed out.
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Affiliation(s)
- Sophie E Jackson
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom.
| | - Antonio Suma
- SISSA, International School for Advanced Studies, via Bonomea 265, I-34136 Trieste, Italy
| | - Cristian Micheletti
- SISSA, International School for Advanced Studies, via Bonomea 265, I-34136 Trieste, Italy.
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29
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Abstract
Spontaneous folding of a polypeptide chain into a knotted structure remains one of the most puzzling and fascinating features of protein folding. The folding of knotted proteins is on the timescale of minutes and thus hard to reproduce with atomistic simulations that have been able to reproduce features of ultrafast folding in great detail. Furthermore, it is generally not possible to control the topology of the unfolded state. Single-molecule force spectroscopy is an ideal tool for overcoming this problem: by variation of pulling directions, we controlled the knotting topology of the unfolded state of the 52-knotted protein ubiquitin C-terminal hydrolase isoenzyme L1 (UCH-L1) and have therefore been able to quantify the influence of knotting on its folding rate. Here, we provide direct evidence that a threading event associated with formation of either a 31 or 52 knot, or a step closely associated with it, significantly slows down the folding of UCH-L1. The results of the optical tweezers experiments highlight the complex nature of the folding pathway, many additional intermediate structures being detected that cannot be resolved by intrinsic fluorescence. Mechanical stretching of knotted proteins is also of importance for understanding the possible implications of knots in proteins for cellular degradation. Compared with a simple 31 knot, we measure a significantly larger size for the 52 knot in the unfolded state that can be further tightened with higher forces. Our results highlight the potential difficulties in degrading a 52 knot compared with a 31 knot.
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30
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Chwastyk M, Cieplak M. Multiple folding pathways of proteins with shallow knots and co-translational folding. J Chem Phys 2016; 143:045101. [PMID: 26233164 DOI: 10.1063/1.4927153] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We study the folding process in the shallowly knotted protein MJ0366 within two variants of a structure-based model. We observe that the resulting topological pathways are much richer than identified in previous studies. In addition to the single knot-loop events, we find novel, and dominant, two-loop mechanisms. We demonstrate that folding takes place in a range of temperatures and the conditions of most successful folding are at temperatures which are higher than those required for the fastest folding. We also demonstrate that nascent conditions are more favorable to knotting than off-ribosome folding.
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Affiliation(s)
- Mateusz Chwastyk
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
| | - Marek Cieplak
- Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
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31
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Szymczak P. Periodic forces trigger knot untying during translocation of knotted proteins. Sci Rep 2016; 6:21702. [PMID: 26996878 PMCID: PMC4800218 DOI: 10.1038/srep21702] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 01/29/2016] [Indexed: 11/19/2022] Open
Abstract
Proteins need to be unfolded when translocated through the pores in mitochondrial and other cellular membranes. Knotted proteins, however, might get stuck during this process, jamming the pore, since the diameter of the pore is smaller than the size of maximally tightened knot. The jamming probability dramatically increases as the magnitude of the driving force exceeds a critical value, Fc. In this numerical study, we show that for deep knots Fc lies below the force range over which molecular import motors operate, which suggest that in these cases the knots will tighten and block the pores. Next, we show how such topological traps might be prevented by using a pulling protocol of a repetitive, on-off character. Such a repetitive pulling is biologically relevant, since the mitochondrial import motor, like other molecular motors transforms chemical energy into directed motions via nucleotide-hydrolysis-mediated conformational changes, which are cyclic in character.
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Affiliation(s)
- Piotr Szymczak
- Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Warsaw, Poland
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32
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Lim NCH, Jackson SE. Molecular knots in biology and chemistry. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:354101. [PMID: 26291690 DOI: 10.1088/0953-8984/27/35/354101] [Citation(s) in RCA: 99] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Knots and entanglements are ubiquitous. Beyond their aesthetic appeal, these fascinating topological entities can be either useful or cumbersome. In recent decades, the importance and prevalence of molecular knots have been increasingly recognised by scientists from different disciplines. In this review, we provide an overview on the various molecular knots found in naturally occurring biological systems (DNA, RNA and proteins), and those created by synthetic chemists. We discuss the current knowledge in these fields, including recent developments in experimental and, in some cases, computational studies which are beginning to shed light into the complex interplay between the structure, formation and properties of these topologically intricate molecules.
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Affiliation(s)
- Nicole C H Lim
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK. Faculty of Sciences, Universiti Brunei Darussalam, Gadong BE 1410, Brunei Darussalam
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Faísca PF. Knotted proteins: A tangled tale of Structural Biology. Comput Struct Biotechnol J 2015; 13:459-68. [PMID: 26380658 PMCID: PMC4556803 DOI: 10.1016/j.csbj.2015.08.003] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Revised: 07/31/2015] [Accepted: 08/07/2015] [Indexed: 01/19/2023] Open
Abstract
Knotted proteins have their native structures arranged in the form of an open knot. In the last ten years researchers have been making significant efforts to reveal their folding mechanism and understand which functional advantage(s) knots convey to their carriers. Molecular simulations have been playing a fundamental role in this endeavor, and early computational predictions about the knotting mechanism have just been confirmed in wet lab experiments. Here we review a collection of simulation results that allow outlining the current status of the field of knotted proteins, and discuss directions for future research.
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Takala H, Björling A, Linna M, Westenhoff S, Ihalainen JA. Light-induced Changes in the Dimerization Interface of Bacteriophytochromes. J Biol Chem 2015; 290:16383-92. [PMID: 25971964 DOI: 10.1074/jbc.m115.650127] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Indexed: 11/06/2022] Open
Abstract
Phytochromes are dimeric photoreceptor proteins that sense red light levels in plants, fungi, and bacteria. The proteins are structurally divided into a light-sensing photosensory module consisting of PAS, GAF, and PHY domains and a signaling output module, which in bacteriophytochromes typically is a histidine kinase (HK) domain. Existing structural data suggest that two dimerization interfaces exist between the GAF and HK domains, but their functional roles remain unclear. Using mutational, biochemical, and computational analyses of the Deinococcus radiodurans phytochrome, we demonstrate that two dimerization interfaces between sister GAF and HK domains stabilize the dimer with approximately equal contributions. The existence of both dimerization interfaces is critical for thermal reversion back to the resting state. We also find that a mutant in which the interactions between the GAF domains were removed monomerizes under red light. This implies that the interactions between the HK domains are significantly altered by photoconversion. The results suggest functional importance of the dimerization interfaces in bacteriophytochromes.
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Affiliation(s)
- Heikki Takala
- From the University of Gothenburg, Department of Chemistry and Molecular Biology, Gothenburg, SE-40530 Sweden and University of Jyvaskyla, Nanoscience Center, Department of Biological and Environmental Sciences, Jyväskylä, FI-40014 Finland
| | - Alexander Björling
- From the University of Gothenburg, Department of Chemistry and Molecular Biology, Gothenburg, SE-40530 Sweden and
| | - Marko Linna
- University of Jyvaskyla, Nanoscience Center, Department of Biological and Environmental Sciences, Jyväskylä, FI-40014 Finland
| | - Sebastian Westenhoff
- From the University of Gothenburg, Department of Chemistry and Molecular Biology, Gothenburg, SE-40530 Sweden and
| | - Janne A Ihalainen
- University of Jyvaskyla, Nanoscience Center, Department of Biological and Environmental Sciences, Jyväskylä, FI-40014 Finland
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Tasinkevych M, Campbell MG, Smalyukh II. Splitting, linking, knotting, and solitonic escape of topological defects in nematic drops with handles. Proc Natl Acad Sci U S A 2014; 111:16268-73. [PMID: 25369931 PMCID: PMC4246280 DOI: 10.1073/pnas.1405928111] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Topologically nontrivial field excitations, including solitonic, linked, and knotted structures, play important roles in physical systems ranging from classical fluids and liquid crystals, to electromagnetism, classic, and quantum field theories. These excitations can appear spontaneously during symmetry-breaking phase transitions. For example, in cosmological theories, cosmic strings may have formed knotted configurations influencing the Early Universe development, whereas in liquid crystals transient tangled defect lines were observed during isotropic-nematic transitions, eventually relaxing to defect-free states. Knotted and solitonic fields and defects were also obtained using optical manipulation, complex-shaped colloids, and frustrated cholesterics. Here we use confinement of nematic liquid crystal by closed surfaces with varied genus and perpendicular boundary conditions for a robust control of appearance and stability of such field excitations. Theoretical modeling and experiments reveal structure of defect lines as a function of the surface topology and material and geometric parameters, establishing a robust means of controlling solitonic, knotted, linked, and other field excitations.
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Affiliation(s)
- Mykola Tasinkevych
- Max-Planck-Institut für Intelligente Systeme, D-70569 Stuttgart, Germany; Institut für Theoretische Physik IV, Universität Stuttgart, D-70569 Stuttgart, Germany;
| | - Michael G Campbell
- Department of Physics, University of Colorado, Boulder, CO 80309; Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO 80309
| | - Ivan I Smalyukh
- Department of Physics, University of Colorado, Boulder, CO 80309; Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO 80309; Department of Electrical, Computer, and Energy Engineering and Materials Science and Engineering Program, University of Colorado, Boulder, CO 80309; and Renewable and Sustainable Energy Institute, National Renewable Energy Laboratory and University of Colorado, Boulder, CO 80309
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36
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He C, Lamour G, Xiao A, Gsponer J, Li H. Mechanically Tightening a Protein Slipknot into a Trefoil Knot. J Am Chem Soc 2014; 136:11946-55. [DOI: 10.1021/ja503997h] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chengzhi He
- Department
of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Guillaume Lamour
- Center
for High Throughput Biology, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Adam Xiao
- Department
of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Joerg Gsponer
- Center
for High Throughput Biology, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Hongbin Li
- Department
of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
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37
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An infrared reporter to detect spatiotemporal dynamics of protein-protein interactions. Nat Methods 2014; 11:641-4. [PMID: 24747815 DOI: 10.1038/nmeth.2934] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Accepted: 02/15/2014] [Indexed: 01/03/2023]
Abstract
We report a protein-fragment complementation assay (PCA) based on the engineered Deinococcus radiodurans infrared fluorescent protein IFP1.4. Unlike previous fluorescent protein PCAs, the IFP PCA is reversible, allowing analysis of spatiotemporal dynamics of hormone-induced signaling complexes in living yeast and mammalian cells at nanometer resolution. The inherently low background of infrared fluorescence permitted detection of subcellular reorganization of a signaling complex expressed at low abundance.
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38
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Stepanenko OV, Bublikov GS, Stepanenko OV, Shcherbakova DM, Verkhusha VV, Turoverov KK, Kuznetsova IM. A knot in the protein structure - probing the near-infrared fluorescent protein iRFP designed from a bacterial phytochrome. FEBS J 2014; 281:2284-98. [PMID: 24628916 DOI: 10.1111/febs.12781] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 02/18/2014] [Accepted: 03/11/2014] [Indexed: 11/30/2022]
Abstract
The possibility of engineering near-infrared fluorescent proteins and biosensors from bacterial phytochrome photoreceptors (BphPs) has led to substantial interest in this family of proteins. The near-infrared fluorescent proteins have allowed non-invasive bio-imaging of deep tissues and whole organs in living animals. BphPs and derived near-infrared fluorescent proteins contain a structural element, called a knot, in their polypeptide chains. The formation of knot structures in proteins was refuted for a long time. Here, we studied the denaturation and renaturation processes of the near-infrared fluorescent probe iRFP, engineered from RpBphP2, which utilizes a heme-derived tetrapyrrole compound biliverdin as a chromophore. iRFP contains a unique figure-of-eight knot. The denaturation and renaturation curves of the iRFP apoform coincided well, suggesting efficient refolding. However, the iRFP holoform exhibited irreversible unfolding and aggregation associated with the bound chromophore. The knot structure in the apoform did not prevent subsequent binding of biliverdin, resulting in the functional iRFP holoform. We suggest that the irreversibility of protein unfolding is caused by post-translational protein modifications, such as chromophore binding, rather than the presence of the knot. These results are essential for future design of BphP-based near-infrared probes, and add important features to our knowledge of protein folding.
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Affiliation(s)
- Olesya V Stepanenko
- Laboratory of Structural Dynamics, Stability and Folding of Proteins, Institute of Cytology, Russian Academy of Sciences, St Petersburg, Russia
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39
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Abstract
Most proteins, in order to perform their biological function, have to fold to a compact native state. The increasing number of knotted and slipknotted proteins identified suggests that proteins are able to manoeuvre around topological barriers during folding. In the present article, we review the current progress in elucidating the knotting process in proteins. Although we concentrate on theoretical approaches, where a knotted topology can be unambiguously detected, comparison with experiments is also reviewed. Numerical simulations suggest that the folding process for small knotted proteins is composed of twisted loop formation and then threading by either slipknot geometries or flipping. As the size of the knotted proteins increases, particularly for more deeply threaded termini, the prevalence of traps in the free energy landscape also increases. Thus, in the case of longer knotted and slipknotted proteins, the folding mechanism is probably supported by chaperones. Overall, results imply that knotted proteins can be folded efficiently and survive evolutionary pressure in order to perform their biological functions.
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40
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Abstract
The forced mechanical unfolding of the knotted protein Human Carbonic Anhydrase (HCA) III is examined by steered, explicit-water molecular dynamics computer simulations. In agreement with previous indications from experiments and coarse-grained simulations, knot tightening by pulling near-terminal amino acids (4 and 267) leads to a much higher resistance to unfolding than for knot untying, where pulling amino acids 4 and 253 untangles the knot by threading the C-terminal end out of the knotting loop. In particular, the resistance during knot tightening is observed to diverge due to a tightly tied-up enzymatic core of the HCA if it is coordinated by the catalytically important zinc ion. The underlying structural pictures are presented and discussed.
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Affiliation(s)
- Joachim Dzubiella
- Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin, Hahn-Meitner Platz 1, 14109 Berlin, Germany
- Department of Physics, Humboldt-University Berlin, Newtonstr. 15, 12489 Berlin, Germany
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41
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Abstract
The backbones of proteins form linear chains. In the case of some proteins, these chains can be characterized as forming linear open knots. The knot type of the full chain reveals only limited information about the entanglement of the chain since, for example, subchains of an unknotted protein can form knots and subchains of a knotted protein can form different types of knots than the entire protein. To understand fully the entanglement within the backbone of a given protein, a complete analysis of the knotting within all of the subchains of that protein is necessary. In the present article, we review efforts to characterize the full knotting complexity within individual proteins and present a matrix that conveys information about various aspects of protein knotting. For a given protein, this matrix identifies the precise localization of knotted regions and shows the knot types formed by all subchains. The pattern in the matrix can be considered as a knotting fingerprint of that protein. We observe that knotting fingerprints of distantly related knotted proteins are strongly conserved during evolution and discuss how some characteristic motifs in the knotting fingerprints are related to the structure of the knotted regions and their possible biological role.
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42
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Abstract
Proteins need to be unfolded when translocated through the pores in mitochondrial and other cellular membranes. Knotted proteins, however, might get stuck during this process since the diameter of the pore is smaller than the size of maximally tightened knot. In the present article, I briefly review the experimental and numerical studies of tight knots in proteins, with a particular emphasis on the estimates of the size of these knots. Next, I discuss the process of protein translocation through the mitochondrial pores and report the results of molecular dynamics simulations of knotted protein translocation, which show how the knot can indeed block the pore.
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43
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He C, Genchev GZ, Lu H, Li H. Mechanically untying a protein slipknot: multiple pathways revealed by force spectroscopy and steered molecular dynamics simulations. J Am Chem Soc 2012; 134:10428-35. [PMID: 22626004 PMCID: PMC3663486 DOI: 10.1021/ja3003205] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein structure is highly diverse when considering a wide range of protein types, helping to give rise to the multitude of functions that proteins perform. In particular, certain proteins are known to adopt a knotted or slipknotted fold. How such proteins undergo mechanical unfolding was investigated utilizing a combination of single molecule atomic force microscopy (AFM), protein engineering, and steered molecular dynamics (SMD) simulations to show the mechanical unfolding mechanism of the slipknotted protein AFV3-109. Our results reveal that the mechanical unfolding of AFV3-109 can proceed via multiple parallel unfolding pathways that all cause the protein slipknot to untie and the polypeptide chain to completely extend. These distinct unfolding pathways proceed via either a two- or three-state unfolding process involving the formation of a well-defined, stable intermediate state. SMD simulations predict the same contour length increments for different unfolding pathways as single molecule AFM results, thus providing a plausible molecular mechanism for the mechanical unfolding of AFV3-109. These SMD simulations also reveal that two-state unfolding is initiated from both the N- and C-termini, while three-state unfolding is initiated only from the C-terminus. In both pathways, the protein slipknot was untied during unfolding, and no tightened slipknot conformation was observed. Detailed analysis revealed that interactions between key structural elements lock the knotting loop in place, preventing it from shrinking and the formation of a tightened slipknot conformation. Our results demonstrate the bifurcation of the mechanical unfolding pathway of AFV3-109 and point to the generality of a kinetic partitioning mechanism for protein folding/unfolding.
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Affiliation(s)
- Chengzhi He
- Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
| | - Georgi Z. Genchev
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, U. S. A
| | - Hui Lu
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, U. S. A
| | - Hongbin Li
- Department of Chemistry, University of British Columbia, Vancouver, BC V6T 1Z1, Canada
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44
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Conservation of complex knotting and slipknotting patterns in proteins. Proc Natl Acad Sci U S A 2012; 109:E1715-23. [PMID: 22685208 DOI: 10.1073/pnas.1205918109] [Citation(s) in RCA: 168] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
While analyzing all available protein structures for the presence of knots and slipknots, we detected a strict conservation of complex knotting patterns within and between several protein families despite their large sequence divergence. Because protein folding pathways leading to knotted native protein structures are slower and less efficient than those leading to unknotted proteins with similar size and sequence, the strict conservation of the knotting patterns indicates an important physiological role of knots and slipknots in these proteins. Although little is known about the functional role of knots, recent studies have demonstrated a protein-stabilizing ability of knots and slipknots. Some of the conserved knotting patterns occur in proteins forming transmembrane channels where the slipknot loop seems to strap together the transmembrane helices forming the channel.
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45
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Dynamics of protein folding and cofactor binding monitored by single-molecule force spectroscopy. Biophys J 2012; 101:2009-17. [PMID: 22004755 DOI: 10.1016/j.bpj.2011.08.051] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 08/23/2011] [Accepted: 08/26/2011] [Indexed: 12/24/2022] Open
Abstract
Many proteins in living cells require cofactors to carry out their biological functions. To reach their functional states, these proteins need to fold into their unique three-dimensional structures in the presence of their cofactors. Two processes, folding of the protein and binding of cofactors, intermingle with each other, making the direct elucidation of the folding mechanism of proteins in the presence of cofactors challenging. Here we use single-molecule atomic force microscopy to directly monitor the folding and cofactor binding dynamics of an engineered metal-binding protein G6-53 at the single-molecule level. Using the mechanical stability of different conformers of G6-53 as sensitive probes, we directly identified different G6-53 conformers (unfolded, apo- and Ni(2+)-bound) populated along the folding pathway of G6-53 in the presence of its cofactor Ni(2+). By carrying out single-molecule atomic force microscopy refolding experiments, we monitored kinetic evolution processes of these different conformers. Our results suggested that the majority of G6-53 folds through a binding-after-folding mechanism, whereas a small fraction follows a binding-before-folding pathway. Our study opens an avenue to utilizing force spectroscopy techniques to probe the folding dynamics of proteins in the presence of cofactors at the single-molecule level, and we anticipated that this method can be used to study a wide variety of proteins requiring cofactors for their function.
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46
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Mishra R, Bhushan S. Knot theory in understanding proteins. J Math Biol 2011; 65:1187-213. [DOI: 10.1007/s00285-011-0488-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 10/20/2011] [Indexed: 11/30/2022]
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47
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Sayre TC, Lee TM, King NP, Yeates TO. Protein stabilization in a highly knotted protein polymer. Protein Eng Des Sel 2011; 24:627-30. [PMID: 21669955 PMCID: PMC3165941 DOI: 10.1093/protein/gzr024] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Revised: 05/10/2011] [Accepted: 05/11/2011] [Indexed: 11/13/2022] Open
Abstract
The polypeptide backbones of a few proteins are tied in a knot. The biophysical effects and potential biological roles of knots are not well understood. Here, we test the consequences of protein knotting by taking a monomeric protein, carbonic anhydrase II, whose native structure contains a shallow knot, and polymerizing it end-to-end to form a deeply and multiply knotted polymeric filament. Thermal stability experiments show that the polymer is stabilized against loss of structure and aggregation by the presence of deep knots.
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Affiliation(s)
- Tobias C. Sayre
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Toni M. Lee
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Neil P. King
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Todd O. Yeates
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
- California Nanosystems Institute, University of California, Los Angeles, CA 90095, USA
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48
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Vierstra RD, Zhang J. Phytochrome signaling: solving the Gordian knot with microbial relatives. TRENDS IN PLANT SCIENCE 2011; 16:417-426. [PMID: 21719341 DOI: 10.1016/j.tplants.2011.05.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Revised: 05/23/2011] [Accepted: 05/25/2011] [Indexed: 05/28/2023]
Abstract
Phytochromes encompass a diverse collection of biliproteins that regulate numerous photoresponses in plants and microorganisms. Whereas the plant versions have proven experimentally intractable for structural studies, the microbial forms have recently provided important insights into how these photoreceptors work at the atomic level. Here, we review the current understanding of these microbial phytochromes, which shows that they have a modular dimeric architecture that propagates light-driven rotation of the bilin to distal contacts between adjacent signal output domains. Surprising features underpinning this signaling include: a deeply buried chromophore; a knot and hairpin loop that stabilizes the photosensing domain; and an extended helical spine that translates conformational changes in the photosensing domain to the output domain. Conservation within the superfamily both in modular construction and sequence strongly suggests that higher plant phytochromes work similarly as light-regulated toggle switches.
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Affiliation(s)
- Richard D Vierstra
- Department of Genetics, 425-G Henry Mall, University of Wisconsin-Madison, Madison, WI 53706, USA.
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49
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Pepłowski L, Sikora M, Nowak W, Cieplak M. Molecular jamming--the cystine slipknot mechanical clamp in all-atom simulations. J Chem Phys 2011; 134:085102. [PMID: 21361557 DOI: 10.1063/1.3553801] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A recent survey of 17 134 proteins has identified a new class of proteins which are expected to yield stretching induced force peaks in the range of 1 nN. Such high force peaks should be due to forcing of a slip-loop through a cystine ring, i.e., by generating a cystine slipknot. The survey has been performed in a simple coarse grained model. Here, we perform all-atom steered molecular dynamics simulations on 15 cystine knot proteins and determine their resistance to stretching. In agreement with previous studies within a coarse grained structure based model, the level of resistance is found to be substantially higher than in proteins in which the mechanical clamp operates through shear. The large stretching forces arise through formation of the cystine slipknot mechanical clamp and the resulting steric jamming. We elucidate the workings of such a clamp in an atomic detail. We also study the behavior of five top strength proteins with the shear-based mechanostability in which no jamming is involved. We show that in the atomic model, the jamming state is relieved by moving one amino acid at a time and there is a choice in the selection of the amino acid that advances the first. In contrast, the coarse grained model also allows for a simultaneous passage of two amino acids.
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Affiliation(s)
- Lukasz Pepłowski
- Institute of Physics, Nicolaus Copernicus University, Torun, Poland
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50
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Zheng P, Cao Y, Li H. Facile method of constructing polyproteins for single-molecule force spectroscopy studies. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:5713-5718. [PMID: 21486060 DOI: 10.1021/la200915d] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Constructing polyproteins consisting of identical tandem repeats of proteins provides an unambiguous method of investigating the mechanical properties of proteins at the single-molecule level using force spectroscopy techniques. Here we report a maleimide-thiol coupling-based facile method of constructing polyproteins for single-molecule force spectroscopy studies on the mechanical properties of proteins. This method allows for the construction of polyproteins in an efficient fashion under room temperature. The resultant thioether bonds are resistant to reduction and make it possible to carry out single-molecule force spectroscopy studies under various redox conditions. This novel method complements existing polyprotein engineering methods and can be easily applied to a wide variety of proteins.
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Affiliation(s)
- Peng Zheng
- Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
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