Computer Modeling of Force-Induced Titin Domain Unfolding

  • Hui Lu
  • André Krammer
  • Barry Isralewitz
  • Viola Vogel
  • Klaus Schulten
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 481)


Titin, a 1 μm long protein found in striated muscle myofibrils, possesses unique elastic and extensibility properties, and is largely composed of a PEVK region and β-sandwich immunoglobulin (Ig) and fibronectin type III (FnIII) domains. The extensibility behavior of titin has been shown in atomic force microscope and optical tweezer experiments to partially depend on the reversible unfolding of individual Ig and Fnlll domains. We performed steered molecular dynamics simulations to stretch single titin Ig domains in solution with pulling speeds of 0.1 – 1.0 Å/ps, and Fnlll domains with a pulling speed of 0.5 Å/ps. Resulting force-extension profiles exhibit a single dominant peak for each domain unfolding, consistent with the experimentally observed sequential, as opposed to concerted, unfolding of Ig and Fnlll domains under external stretching forces. The force peaks can be attributed to an initial burst of a set of backbone hydrogen bonds connected to the domains’ terminal β-strands. Constant force stretching simulations, applying 500 – 1000 pN of force, were performed on Ig domains. The resulting domain extensions are halted at an initial extension of 10 Å until the set of all six hydrogen bonds connecting terminal β-strands break simultaneously. This behavior is accounted for by a barrier separating folded and unfolded states, the shape of which is consistent with AFM and chemical denaturation data.


Atomic Force Microscopy Rupture Force Atomic Force Microscopy Data Atomic Force Microscopy Experiment Steer Molecular Dynamics Simulation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Allen MP, Tildesley DJ. Computer Simulation of Liquids. New York: Oxford University Press, 1987.Google Scholar
  2. Beer JH, Springer KT, Coller BS. Immobilized Arg-Gly-Asp (RGD) peptides of varying lengths as structural probes of the platelet glycoprotein IIb/IIIa receptor. Blood 1992;79:117–128.PubMedGoogle Scholar
  3. Brooks BR, Bruccoleri RE, Olafson BD, States DJ, Swaminathan S, Karplus M. CHARMM: A program for macromolecular energy, minimization, and dynamics calculations. J Comp Chem 1983;4:187–217.CrossRefGoogle Scholar
  4. Brünger AT. X-PLOR, (Version 3.1): A System for X-ray Crystallography and NMR. New Haven CT: Yale University Press, 1992.Google Scholar
  5. Carrion-Vazquez M, Oberhauser AF, Fowler SB, Marszalek PE, Broedel SE, Clarke J, Fernandez JM. Mechanical and chemical unfolding of a single protein: A comparison. Proc Natl Acad Sci USA 1999;96:3694–3699.PubMedCrossRefGoogle Scholar
  6. Erickson HP. Reversible unfolding of fibronectin type III and immunoglobulin domains provides the structural basis for stretch and elasticity of titin and fibronectin. Proc Natl Acad Sci USA 1994,91:10114–10118.PubMedCrossRefGoogle Scholar
  7. Evans E, Ritchie K. Strength of a weak bond connecting flexible polymer chains. Biophys J 1999;76:2439–2447.PubMedCrossRefGoogle Scholar
  8. Granzier H, Helmes M, Trombitás K. Nonuniform elasticity of titin in cardiac myocytes: a study using immunoelectron microscopy and cellular mechanics. Biophys J 1996;70:430–442.PubMedCrossRefGoogle Scholar
  9. Greaser ML, Sebestyen MG, Fritz JD, Wolff JA. cDNAsequence of rabbit cardiac titin/connectin. Adv Biophys 1996;33:13–25.PubMedCrossRefGoogle Scholar
  10. Grubmüller H, Heymann B, Tavan P. Ligand binding: molecular mechanics calculation of the streptavidin-biotin rupture force. Science 1996,271:997–999.PubMedCrossRefGoogle Scholar
  11. Gullingsrud J, Braun R, Schulten K. Reconstructing potentials of mean force through time series analysis of steered molecular dynamics simulations. J Comp Phys 1999;151:190–211.CrossRefGoogle Scholar
  12. Humphrey WF, Dalke A, Schulten K. VMD — Visual Molecular Dynamics. J Mol Graphics 1996;14:33–38.CrossRefGoogle Scholar
  13. Improta S, Politou AS, Pastore A. Immunoglobulin-like modules from titin I-band: extensible components of muscle elasticity. Structure 1996;4:323–337.PubMedCrossRefGoogle Scholar
  14. Isralewitz B, Izrailev S, Schulten K. Binding pathway of retinal to bacterio-opsin: a prediction by molecular dynamics simulations. Biophys J 1997;73:2972–2979.PubMedCrossRefGoogle Scholar
  15. Izrailev S, Stepaniants S, Baisera M, Oono Y, Schulten K. Molecular dynamics study of unbinding of the avidin-biotin complex. Biophys J 1997;72:1568–1581.PubMedCrossRefGoogle Scholar
  16. Izrailev S, Stepaniants S, Isralewitz B, Kosztin D, Lu H, Molnar F, Wriggers W, Schulten K. “Steered molecular dynamics.” In Computational Molecular Dynamics: Challenges, Methods, Ideas, volume 4 of Lecture Notes in Computational Science and Engineering, P Deuflhard, J Hermans, B Leimkuhler, AE Mark, S Reich, RD Skeel, eds. Berlin: Springer-Verlag 1998;39–65.Google Scholar
  17. Jorgensen WL, Chandrasekhar J, Madura JD, Impey RW, Klein ML. Comparison of simple potential functions for simulating liquid water. J Chem Phys 1983;79:926–935.CrossRefGoogle Scholar
  18. Kellermayer MS, Granzier HL. Elastic properties of single titin molecules made visible through fluorescent F-actin binding. Biochem Biophys Res Commun 1996;221:491–497.PubMedCrossRefGoogle Scholar
  19. Kellermayer MS, Smith SB, Granzier HL, Bustamante C. Folding-unfolding transition in single titin modules characterized with laser tweezers. Science 1997;276:1112–1116.PubMedCrossRefGoogle Scholar
  20. Kosztin D, Izrailev S, Schulten K. Unbinding of retinoic acid from its receptor studied by steered molecular dynamics. Biophys J 1999;76:188–197.PubMedCrossRefGoogle Scholar
  21. Krammer A, Lu H, Isralewitz B, Schulten K, Vogel V. Forced unfolding of the fibronectin type III module reveals a tensile molecular recognition switch. Proc Nail Acad Sci USA 1999;96:1351–1356.CrossRefGoogle Scholar
  22. Labeit S, Kolmerer B, Linke WA. The giant protein titin. Emerging roles in physiology and pathophysiology. Circ Res 1997;80:290–294.PubMedCrossRefGoogle Scholar
  23. Labeit S, Kolmerer B. Titins, giant proteins in charge of muscle ultrastructure and elasticity. Science 1995;270:293–296.PubMedCrossRefGoogle Scholar
  24. Leahy DJ, Aukhil I, Erickson HP. 2.0 Å crystal structure of a four-domain segment of human fibronectin encompassing the RGD loop and synergy region. Cell 1996;84:155–164.PubMedCrossRefGoogle Scholar
  25. Linke WA, Popov VI, Pollack GH. Passive and active tension in single cardiac myofibrils. Biophys J 1994;67:782–792.PubMedCrossRefGoogle Scholar
  26. Lu H, Isralewitz B, Krammer A, Vogel V, Schulten K. Unfolding of titin immunoglobulin domains by steered molecular dynamics simulation. Biophys J 1998;75:662–671.PubMedCrossRefGoogle Scholar
  27. Lu H, Schulten K. Steered molecular dynamics simulation of conformational changes of immunoglobulin domain 127 interpret atomic force microscopy observations. Chem Phys 1999a;247:141–153.CrossRefGoogle Scholar
  28. Lu H, Schulten K. Steered molecular dynamics simulations of force-induced protein domain unfolding. Proteins Struct Funct Genet1999b;35:453–463.PubMedCrossRefGoogle Scholar
  29. Machado C, Sunkel CE, Andrew DJ. Human autoantibodies reveal titin as a chromosomal protein. J Cell Biol 1998;141:321–333.PubMedCrossRefGoogle Scholar
  30. MacKerell AD Jr, Bashford D, Bellott M, Dunbrack RL Jr, Evanseck J, Field MJ, Fischer S, Gao J, Guo H, Ha S, Joseph D, Kuchnir L, Kuczera K, Lau FTK, Mattos C, Michnick S, Ngo T, Nguyen DT, Prodhom B, Reiher IWE, Roux B, Schlenkrich M, Smith J, Stote R, Sträub J, Watanabe M, Wiorkiewicz-Kuczera J, Yin D, Karplus M. All-hydrogen empirical potential for molecular modeling and dynamics studies of proteins using the CHARMM22 force field. J Phys Chem B 1998;102:3586–3616.CrossRefGoogle Scholar
  31. Marrink SJ, Berger O, Tieleman P, Jähnig F. Adhesion forces of lipids in a phospholipid membrane studied by molecular dynamics simulations. Biophys J 1998;74:931–943.PubMedCrossRefGoogle Scholar
  32. Maruyama K. Connectin/titin, giant elastic protein of muscle. FASEB J 1997;11:341–345.PubMedGoogle Scholar
  33. Nelson MT, Humphrey W, Gursoy A, Dalke A, Kalé LV, Skeel RD, Schulten K. NAMD: a parallel, object-oriented molecular dynamics program. Int J Supercomput Appl High Perform Comput 1996;10:251–268.CrossRefGoogle Scholar
  34. Oberhauser AF, Marszalek PE, Erickson HP, Fernandez JM. The molecular elasticity of the extracellular matrix protein tenascin. Nature 1998;393:181–185.PubMedCrossRefGoogle Scholar
  35. Paci E, Karplus M. Forced unfolding of fibronectin type 3 modules: An analysis by biased molecular dynamics simulations. J Mol Biol 1999;288:441–459.PubMedCrossRefGoogle Scholar
  36. Politou AS, Thomas DJ, Pastore A. The folding and stability of titin immunoglobulin-like modules, with implications for mechanism of elasticity. Biophys J 1995;69:2601–2610.PubMedCrossRefGoogle Scholar
  37. Rief M, Gautel M, Oesterhelt F, Fernandez JM, Gaub HE. Reversible unfolding of individual titin immunoglobulin domains by AFM. Science 1997;276:1109–1112.PubMedCrossRefGoogle Scholar
  38. Rief M, Gautel M, Schemmel A, Gaub HE. The mechanical stability of immunoglobulin and fibronectin III domains in the muscle protein titin measured by atomic force microscopy. Biophys J 1998;75:3008–3014.PubMedCrossRefGoogle Scholar
  39. Rief M, Pascual J, Saraste M, Gaub HE. Single molecule force spectroscopy of spectrin repeats: Low unfolding forces in helix bundles. J Mol Biol 1999;286:553–561.PubMedCrossRefGoogle Scholar
  40. Rohs R, Etchebest C, Lavery R. Unraveling proteins: a molecular mechanics study. Biophys J 1999;76:2760–2768.PubMedCrossRefGoogle Scholar
  41. Schulten K, Schulten Z, Szabo A. Dynamics of reactions involving diffusive barrier crossing. J Chem Phys 1981;74:4426–4432.CrossRefGoogle Scholar
  42. Schulten K, Schulten Z, Szabo A. Reactions governed by a binomial redistribution process-the Ehrenfest urn problem. Physica 1980;100A:599–614.Google Scholar
  43. Socci ND, Onuchic JN, Wolynes PG. Stretching lattice models of protein folding. Proc Natl Acad Sci USA 1999;96:2031–2035.PubMedCrossRefGoogle Scholar
  44. Stepaniants S, Izrailev S, Schulten K. Extraction of lipids from phospholipid membranes by steered molecular dynamics. J Mol Model 1997;3:473–475.CrossRefGoogle Scholar
  45. Szabo A, Schulten K, Schulten Z. First passage time approach to diffusion controlled reactions. J Chem Phys 1980;72:4350–4357.CrossRefGoogle Scholar
  46. Tskhovrebova L, Trinick J, Sleep JA, Simmons RM. Elasticity and unfolding of single molecules of the giant protein titin. Nature 1997;387:308–312.PubMedCrossRefGoogle Scholar
  47. Wang K, McCarter R, Wright J, Beverly J, Ramirez-Mitchell R. Viscoelasticity of the sarcomere matrix of skeletal muscles. Biophys J 1993;64:1161–1177.PubMedCrossRefGoogle Scholar
  48. Wriggers W, Schulten K. Investigating a back door mechanism of actin phosphate release by steered molecular dynamics. Proteins Struct Funct Genet 1999;35:262–273.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 2000

Authors and Affiliations

  • Hui Lu
    • 1
  • André Krammer
    • 2
  • Barry Isralewitz
    • 1
  • Viola Vogel
    • 2
  • Klaus Schulten
    • 1
  1. 1.Beckman Institute for Advanced Science and TechnologyUniversity of Illinois at Urbana-ChampaignUrbanaUSA
  2. 2.Departments of Physics and BioengineeringUniversity of WashingtonSeattleUSA

Personalised recommendations