Structure and Assembly of Type IV Pilins

Katrina T. Forest

doi:10.1128/9781555818395.ch6

Chapter 6 : Structure and Assembly of Type IV Pilins

Author: Katrina T. Forest¹

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Affiliations: 1: Department of Bacteriology, University of Wisconsin—Madison, Madison, WI 53706

Content Type: Monograph

Publication Year: 2005

Category: Microbial Genetics and Molecular Biology; Bacterial Pathogenesis

Book DOI: 10.1128/9781555818395

Chapter DOI: 10.1128/9781555818395.ch6

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Abstract:

This chapter focuses on the contribution of structural biology to the understanding of the type IV pili. Recent reviews cover the developments in research on molecular genetics, regulation of expression and assembly, pilus-mediated surface motility, host responses to pili, and pilus-based vaccines carried out by many laboratories around the world. High-resolution structures of four type IV pilins have been published. In the chapter, the structural details of each pilin subunit are elaborated and compared. Models for pilus filament assembly based on the monomer structures are also discussed. The limited structural information available for pilus assembly proteins is summarized. The chapter is an appropriate venue in which to clarify that type IV pilus filament models are not refined atomic resolution structures of pilus quatenary assemblies. To increase the accuracy and resolution of any type IV pilus assembly model, the model must be rigorously refined against moderate-resolution data for intact pili, such as cryoelectron microscopy reconstructions or complete high-resolution fiber diffraction data sets. These have been challenging to obtain for the very smooth and thin type IV pili. X-ray crystallography on additional pilin subunits, high-resolution electron microscopy reconstructions of intact pilus filaments, and structural biology of additional proteins in the type IV pilus pathway are clearly important next steps for understanding the mechanisms of pilus assembly, retraction, and function.

Citation: Forest K. 2005. Structure and Assembly of Type IV Pilins, p 81-100. In Waksman G, Caparon M, Hultgren S (ed), Structural Biology of Bacterial Pathogenesis. ASM Press, Washington, DC. doi: 10.1128/9781555818395.ch6

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Structure and Assembly of Type IV Pilins

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Figure 1

Pilin structure-based sequence alignment. (a) Sequences of V. cholerae TcpA, N. gonorrhoeae MS11 pilin (GC), P. aeruginosa strain K122-4 pilin, and P. aeruginosa PAK pilin are aligned based on the three-dimensional structures. Sequence identity (grey shading if three of four residues are the same) is evident in the N-terminal half of the boxed α1-helix. Secondary-structure elements below each sequence highlight the structurally conserved β-sheet (solid arrows) and disulfide bond (reverse video). Species-specific β-strands (dashed arrows) and helices (wavy boxes) occur largely in the αβ loop and D-region. Amino acids contributing to species-specific functionalities are in bold italics. TcpA residues involved in crystal packing and fiberstabilizing hydrophobic interactions (Y51, P58, A59, T60, K68, L69, G72, L73, L76, G77, K121, L176, T177, I179, V182, and L185); the MS11 glycosylation site (S63), phosphorylation site (S68), and hypervariable region (residues 128 to 141); the PAK and K122-4 receptorbinding loops (residues 131 to 144); and the K122-4 second disulfide bond (C57 to C93) are shown. (b) Conserved α/β-roll pilin fold, with the locations of species-specific αβ loop and D-region shown schematically.

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Figure 1

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Figure 2

Structure of the N. meningitidis outer membrane secretin PilQ as determined by negative-stain electron microscopy reconstruction with 12–fold averaging. (A) Top-down view showing the central cavity; overall width, 155 Å. (B) Side-on view, rotated 90° about the x axis from panel A; overall height, 120 Å. R and P indicate the ring and plug regions, respectively. Reprinted from Collins et al. (2003) with permission.

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Figure 2

References

/content/book/10.1128/9781555818395.chap6

1. Aas, F. E.,, M. Wolfgang,, S. Frye,, S. Dunham,, C. Lovold,, and M. Koomey. 2002. Competence for natural transformation in Neisseria gonorrhoeae: components of DNA binding and uptake linked to type IV pilus expression. Mol. Microbiol. 46: 749– 760.

2. Alm, R. A.,, and J. S. Mattick. 1997. Genes involved in the biogenesis and function of type-4 fimbriae in Pseudomonas aeruginosa. Gene 192: 89– 98.

3. Audette, G. F. 2003. Purification, crystallization and preliminary diffraction studies of the Pseudomonas aeruginosa strain K122-4 monomeric pilin. Acta Crystallogr. Ser. D 59: 1665– 1667.

4. Bieber, D.,, S. W. Ramer,, C.-Y. Wu,, W. J. Murray,, T. Tobe,, R. Fernandez,, and G. Schoolnik. 1998. Type IV pili, transient bacterial aggregates, and virulence of enteropathogenic Escherichia coli. Science 280: 2114– 2118.

5. Boslego, J. W.,, E. C. Tramont,, R. C. Chung,, D. G. McChesney,, J. Ciak,, J. C. Sadoff,, M. V. Piziak,, J. D. Brown,, C. C. Brinton, Jr.,, S. W. Wood, et al. 1991. Efficacy trial of a parenteral gonococcal pilus vaccine in man. Vaccine 9: 154– 162.

6. Bradley, D. E. 1980. A function of Pseudomonas aeruginosa PAO polar pili: twitching motility. Can. J. Microbiol. 26: 146– 154.

7. Bullitt, E.,, and L. Makowski. 1998. Bacterial adhesion pili are heterologous assemblies of similar subunits. Biophys. J. 74: 623– 632.

8. Cachia, P. J.,, and R. S. Hodges. 2003. Synthetic peptide vaccine and antibody therapeutic development: prevention and treatment of Pseudomonas aeruginosa. Biopolymers 71: 141– 168.

9. Cohen-Krausz, S.,, and S. Trachtenberg. 2002. The structure of the archeabacterial flagellar filament of the extreme halophile Halobacterium salinarum R1M1 and its relation to eubacterial flagellar filaments and type IV pili. J. Mol. Biol. 321: 383– 395.

10. Collins, R. F.,, L. Davidsen,, J. P. Derrick,, R. C. Ford,, and T. Tonjum. 2001. Analysis of the PilQ secretin from Neisseria meningitidis by transmission electron microscopy reveals a dodecameric quaternary structure. J. Bacteriol. 183: 3825– 3832.

11. Collins, R. F.,, R. C. Ford,, A. Kitmitto,, R. O. Olsen,, T. Tonjum,, and J. P. Derrick. 2003. Three-dimensional structure of the Neisseria meningitidis secritein PilQ determined from negative-stain transmission electron microscopy. J. Bacteriol. 185: 2611– 2617.

12. Comolli, J. C.,, L. L. Waite,, K. E. Mostov,, and J. N. Engel. 1999. Pili binding to asialo-GM1 on epithelial cells can mediate cytotoxicity or bacterial internalizatin by Pseudomonas aeruginosa. Infect. Immun. 67: 3207– 3214.

13. Craig, L.,, M. E. Pique,, and J. A. Tainer. 2004. Type IV pilus structure and bacterial pathogenicity. Nat. Rev. Microbiol. 2: 363– 378.

14. Craig, L.,, R. K. Taylor,, M. E. Pique,, B. D. Adair,, A. S. Arvai,, M. Singh,, S. J. Lloyd,, D. S. Shin,, E. D. Getzoff,, M. Yeager,, K. T. Forest,, and J. A. Tainer. 2003. Type IV pilin structure and assembly: X-ray and EM analyses of Vibrio cholerae toxin-coregulated pilus and Pseudomonas aeruginosa PAK pilin. Mol. Cell 11: 1139– 1150.

15. Dupuy, B.,, and A. P. Pugsley. 1994. Type IV prepilin peptidase gene of Neisseria gonorrhoeae MS11: presence of a related gene in other piliated and nonpiliated Neisseria strains. J. Bacteriol. 176: 1323– 1331.

16. Folkhard, W.,, D. A. Marvin,, T. H. Watts,, and W. Paranchych. 1981. Structure of polar pili from Pseudomonas aeruginosa strains K and O. J. Mol. Biol. 149: 79– 93.

17. Forest, K. T.,, S. L. Bernstein,, E. D. Getzoff,, M. So,, G. Tribbick,, H. M. Geysen,, C. D. Deal,, and J. A. Tainer. 1996. Assembly and antigenicity of the N. gonorrhoeae pilus mapped with antibodies. Infect. Immun. 64: 644– 652.

18. Forest, K. T.,, S. J. Dunham,, M. Koomey,, and J. A. Tainer. 1999. Crystallographic structure of phosphorylated pilin from Neisseria: phosphoserine sites modify type IV pilus surface chemistry and morphology. Mol. Microbiol. 31: 743– 752.

19. Forest, K. T.,, K. A. Satyshur,, G. A. Worzalla,, J. K. Hansen,, and T. J. Herdendorf. 2004. The pilus-retraction protein PilT: ultrastructure of the biological assembly. Acta Crystallogr. D 60: 978– 982.

20. Forest, K. T.,, and J. A. Tainer,. 1997a. Type IV pilin structure, assembly and immunodominance:applications to vaccine design, p. 167– 173. In F. Brown,, D. Burton,, P. Doherty,, J. J. Mekalanos,, and E. Norrby (ed.), Vaccines 97:Molecular Approaches to the Control of Infectious Diseases. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.

21. Forest, K. T.,, and J. A. Tainer. 1997b. Type-4 pilus structure: outside to inside and top to bottom—a minireview. Gene 192: 165– 169.

22. Friedrich, A.,, C. Prust,, T. Hartsch,, A. Henne,, and B. Averhoff. 2002. Molecular analyses of the natural transformation machinery and identification of pilus structures in the extremely thermophilic bacterium Thermus thermophilus strain HB27. Appl. Environ. Microbiol. 68: 745– 755.

23. Gonzalez, A.,, C. Nave,, and D. A. Marvin. 1995. Pf1 filamentous bacteriophage: refinement of a molecular model by simulated annealing using 3.3 Å resolution X-ray fibre diffraction data. Acta Crystallogr. Ser. D 51: 792– 804.

24. Hazes, B.,, P. A. Sastry,, K. Hayakawa,, R. J. Read,, and R. T. Irwin. 2000. Crystal structure of Pseudomonas aeruginosa PAK pilin suggests a main-chain-dominated mode of receptor binding. J. Mol. Biol. 299: 1005– 1017.

25. Hegge, F. T.,, P. G. Hitchen,, F. E. Aas,, H. Kristiansen,, C. Lovold,, W. Egge-Jacobsen,, M. Panico,, W. Y. Leong,, V. Bull,, M. Virji,, H. R. Morris,, A. Dell,, and M. Koomey. 2004. Unique modifications with phosphocholine and phosphoethanolamine define alternate antigenic forms of Neisseria gonorrhoeae type IV pili. Proc. Natl. Acad. Sci. USA 101: 10798– 10803.

26. Herdendorf, T. J.,, D. McCaslin,, and K. T. Forest. 2002. A. aeolicus PilT, homologue of a twitching motility protein, is an oligomeric ATPase. J. Bacteriol. 184: 6465– 6471.

27. Herrington, D. A.,, R. H. Hall,, G. Losonsky,, J. J. Mekalanos,, R. K. Taylor,, and M. M. Levine. 1988. Toxin, toxin-coregulated pilus, and the toxR regulon are essential for Vibrio cholerae pathogenesis in humans. J. Exp. Med. 168: 1487– 1492.

28. Hertle, R.,, R. Mrsny,, and D. J. Fitzgerald. 2001. Dual-function vaccine for Pseudomonas aeruginosa: characterization of chimeric exotoxin A-pilin protein. Infect. Immun. 69: 6962– 6969.

29. Hopfner, K. P.,, L. Craig,, G. Moncalian,, R. A. Zinkel,, T. Usui,, B. A. Owen,, A. Karcher,, B. Henderson,, J. L. Bodmer,, C. T. McMuray,, J. H. Petrini,, and J. A. Tainer. 2002. The Rad50 zinc-hook is a structure joining Mre11 complexes in DNA recombination and repair. Nature 418: 562– 566.

30. Kabsch, W.,, H. G. Mannherz,, D. Suck,, E. F. Pai,, and K. C. Holmes. 1990. Atomic structure of the actin:DNAse I complex. Nature 347: 37– 43.

31. Kaiser, D. 2000. Bacterial motility: how do pili pull? Curr. BIol. 10: R777– R780.

32. Källström, H.,, M. S. Islam,, P. O. Berggren,, and A. B. Jonsson. 1998. Cell signaling by the type IV pili of pathogenic Neisseria. J. Biol. Chem. 273: 21777– 21782.

33. Källström, H.,, M. K. Liszewski,, J. P. Atkinson,, and A. B. Jonsson. 1997. Membrane cofactor protein is a cellular pilus receptor for pathogenic Neisseria. Mol. Microbiol. 25: 639– 647.

34. Kang, Y.,, H. Liu,, S. Genin,, M. A. Schell,, and T. P. Denny. 2002. Ralstonia solanacearum requires type 4 pili to adhere to multiple surfaces and for natural transformation and virulence. Mol. Microbiol. 46: 427– 437.

35. Keizer, D. W.,, C. M. Slupsky,, M. Kalisiak,, A. P. Campbell,, M. P. Crump,, P. A. Sastry,, B. Hazes,, R. T. Irvin,, and B. D. Sykes. 2001. Structure of a pilin monomer from Pseudomonas aeruginosa—implications for the assembly of pili. J. Biol. Chem. 276: 24186– 24193.

36. Kirn, T. J.,, M. J. Lafferty,, C. M. P. Sandoe,, and R. K. Taylor. 2000. Delineation of pilin domains required for bacterial association into microcolonies and intestinal colonization by Vibrio cholerae. Mol. Microbiol. 35: 896– 910.

37. Leiman, P. G.,, M. M. Shneider,, V. A. Kostyuchenko,, P. R. Chipman,, V. V. Mesyanzhinov,, and M. G. Rossmann. 2003. Structure and location of gene product 8 in the bacteriophage T4 baseplate. J. Mol. Biol. 328: 821– 833.

38. Li, Y.,, H. Sun,, X. Ma,, A. Lu,, R. Lux,, D. Zusman,, and W. Shi. 2003. Extracellular polysaccharides mediate pilus retraction during social motility of Myxococcus xanthus. Proc. Natl. Acad. Sci. USA 100: 5443– 5448.

39. Maier, B.,, L. Potter,, M. So,, H. S. Seifert,, and M. P. Sheetz. 2002. Single pilus motor forces exceed 100 pN. Proc. Natl. Acad. Sci. USA 99: 16012– 16017.

40. Marceau, M.,, K. T. Forest,, J. A. Tainer,, and X. Nassif. 1998. Role of O-linked glycosylation of meningococcal type IV pilin for piliation and pilus-mediated adhesion. Mol. Microbiol. 27: 705– 715.

41. Marceau, M.,, and X. Nassif. 1999. Role of glycosylation at Ser63 in production of soluble pilin in pathogenic Neisseria. J. Bacteriol. 181: 656– 661.

42. Marvin, D. A. 1998. Filamentous phage structure, infection and asembly. Curr. Opin. Struct. Biol. 8: 150– 158.

43. Mattick, J. S. 2002. Type IV pili and twitching motility. Annu. Rev. Microbiol. 56: 289– 314.

44. McBride, M. J. 2001. Bacterial gliding motility: multiple mechanisms for cell movement over surfaces. Annu. Rev. Microbiol. 55: 49– 75.

45. McInnes, C.,, F. D. Soennichsen,, C. M. Kay,, R. S. Hodges,, and B. D. Sykes. 1993. NMR solution structure and flexibility of a peptide antigen representing the receptor binding domain of Pseudomonas aeruginosa. Biochemistry 32: 13432– 13440.

46. Meeks, M. D.,, T. K. Wade,, R. K. Taylor,, and W. F. Wade. 2001. Immune response genes modulate serologic responses to Vibrio cholerae TcpA pilin peptides. Infect. Immun. 69: 7687– 7694.

47. Merz, A. J.,, and K. T. Forest. 2002. Bacterial surface motility: slime trails, grappling hooks and nozzles. Curr. Biol. 12: R297– R303.

48. Merz, A. J.,, D. B. Rifenbery,, C. G. Arvidson,, and M. So. 1996. Traversal of a polarized epithelium by pathogenic neisseriae: facilitation by type IV pili and maintenance of epithelial barrier function. Mol. Med. 2: 745– 754.

49. Merz, A. J.,, and M. So. 2000. Interactions of pathogenic neisseriae with epithelial cell membranes. Annu. Rev. Cell Dev. Biol. 16: 423– 457.

50. Merz, A. J.,, M. So,, and M. P. Sheetz. 2000. Pilus retraction powers bacterial twitching motility. Nature 407: 98– 102.

51. Namba, K.,, R. Pattanayek,, and G. Stubbs. 1989. Visualization of protein-nucleic acid interactions in a virus. Refined structure of intact tobacco mosaic virus at 2.9 Å resolution by X-ray fiber diffraction. J. Mol. Biol. 208: 307– 325.

52. Nassif, X.,, C. Pujol,, P. Mornad,, and E. Eugene. 1999. Interactions of pathogenic Neisseria with host cells. Is it possible to assemble the puzzle? Mol. Microbiol. 32: 1124– 1132.

53. Okamoto, S.,, and M. Ohmori. 2002. The cyanobacterial PilT protein responsible for cell motility and transformation hydrolyzes ATP. Plant Cell Physiol. 43: 1127– 1136.

54. O’Toole, G. A.,, and R. Kolter. 1998. Flagellar and twitching motility are necessary for Pseudomonas aeruginosa biofilm development. Mol. Microbiol. 30: 295– 304.

55. Parge, H. E.,, S. L. Bernstein,, C. D. Deal,, D. E. McRee,, D. Christensen,, M. A. Capozza,, B. W. Kays,, T. M. Fieser,, D. Draper,, M. So,, E. D. Getzoff,, and J. A. Tainer. 1990. Biochemical purification and crystallographic characterization of the fiber-forming protein pilin from Neisseria gonorrhoeae. J. Biol. Chem. 265: 2278– 2285.

56. Parge, H. E.,, K. T. Forest,, M. J. Hickey,, D. A. Christensen,, E. D. Getzoff,, and J. A. Tainer. 1995. Structure of the fibre-forming protein pilin at 2.6 Å resolution. Nature 378: 32– 38.

57. Planet, P. J.,, S. C. Kachlany,, R. DeSalle,, and D. H. Figurski. 2001. Phylogeny of genes encoded for secretion NTPases: identification of the widespread tadA subfamily and development of a diagnostic key for gene classification. Proc. Natl. Acad. Sci. USA 98: 2503– 2508.

58. Power, P. M.,, L. F. Roddam,, K. Rutter,, S. Z. Fitzpatrick,, Y. N. Srikhanta,, and M. P. Jennings. 2003. Genetic characterization of pilin glycosylation and phase variation in Neisseria meningitidis. Mol. Microbiol. 49: 833– 847.

59. Pujol, C.,, E. Eugene,, M. Marceau,, and X. Nassif. 1999. The meningococcal PilT protein is required for induction of intimate attachment to epithelial cells following pilus-mediated adhesion. Proc. Natl. Acad. Sci. USA 96: 4017– 4022.

60. Rayment, I.,, W. R. Rypniewski,, K. Schmidt-Base,, R. Smith,, D. R. Tomchick,, M. M. Benning,, D. A. Winkelmann,, G. Wesenberg,, and H. M. Holden. 1993. Three-dimensional structure of myosin subfragment-1: a molecular motor. Science 261: 50– 58.

61. Robien, M. A.,, B. E. Krumm,, M. Sandkvist,, and W. G. J. Hol. 2003. Crystal structure of the extracellular protein secretion NTPase EpsE of Vibrio cholerae. J. Mol. Biol. 333: 657– 674.

62. Russel, M.,, N. A. Linderoth,, and A. Sali. 1997. Filamentous phage assembly: variation on a protein export theme. Gene 192: 23– 32.

63. Samatey, F. A.,, K. Imada,, F. Vonderviszt,, Y. Shirakihara,, and K. Namba. 2000. Crystallization of the F41 fragment of flagellin and data collection from extremely thin crystals. J. Struct. Biol. 132: 106– 111.

64. Schutt, C. E.,, J. C. Myslik,, M. D. Rozycki,, N. C. W. Goonesekere,, and U. Lindberg. 1993. The structure of crystalline profilin:β-actin. Nature 365: 810– 816.

65. Serkin, C. D.,, and H. S. Seifert. 1998. Frequency of pilin antigenic variation in Neisseria gonorrhoeae. J. Bacteriol. 180: 1955– 1959.

66. Skerker, J. M.,, and H. C. Berg. 2001. Direct obervation of extension and retraction of type IV pili. Proc. Natl. Acad. Sci. USA 98: 6901– 6904.

67. Soto, G.,, and S. J. Hultgren. 1999. Bacterial adhesins: common themes and variations in architecture and assembly. J. Bacteriol. 181: 1059– 1071.

68. Stimson, E.,, M. Virji,, S. Barker,, M. Panico,, I. Blench,, J. Saunders,, G. Payne,, E. R. Moxon,, A. Dell,, and H. R. Morris. 1996. Discovery of a novel protein modification: α-glycerophosphate is a substituent of meningococcal pilin. Biochem. J. 316: 29– 33.

69. Stimson, E.,, M. Virji,, K. Makepeace,, A. Dell,, H. R. Morris,, G. Payne,, J. R. Saunders,, M. P. Jennings,, S. Barker,, M. Panico,, I. Blench,, and E. R. Moxon. 1995. Meningococcal pilin: a glycoprotein substituted with digalactosyl-2,4-diacetamido-2,4,6-trideoxyhexose. Mol. Microbiol. 17: 1201– 1214.

70. VanLoock, M. S.,, X. Yu,, S. Yang,, A. L. Lai,, C. Low,, M. J. Campbell,, and E. H. Egelman. 2003. ATPmediated conformational changes in the RecA filament. Structure 11: 187– 196.

71. Vorobiev, S.,, B. Strolopytov,, D. G. Drubin,, C. Frieden,, S. Ono,, J. Condeelis,, P. A. Rubenstein,, and S. C. Almo. 2003. The structure of nonvertebrate actin: implications for the ATP hydrolytic mechanism. Proc. Natl. Acad. Sci. USA 100: 5760– 5765.

72. Watts, T. H.,, C. M. Kay,, and W. Paranchych. 1983. Spectral properties of three quaternary arrangements of Pseudomonas pilin. Biochemistry 22: 3640– 3646.

73. Winther-Larsen, H. C.,, F. T. Hegge,, M. Wolfgang,, S. F. Hayes,, J. P. van Putten,, and M. Koomey. 1998. Neisseria gonorrhoeae PilV, a type IV pilus-associated protein essential to human epithelial cell adherence. Proc. Natl. Acad. Sci. USA 98: 15276– 15281.

74. Wolfgang, M.,, J. P. van Putten,, S. F. Hayes,, and J. M. Koomey. 1999. The comP locus of Neisseria gonorrhoeae encodes a type IV prepilin that is dispensable for pilus biogenesis but essential for natural transformation. Mol. Microbiol. 31: 1345– 1357.

75. Wong, W. Y.,, A. P. Campbell,, C. McInnes,, B. D. Sykes,, W. Paranchych,, R. T. Irvin,, and R. S. Hodges. 1995. Structure-function analysis of the adherence-binding domain on the pilin of Pseudomonas aeruginosa strains PAK and KB7. Biochemistry 34: 12963– 12972.

76. Wu, J. Y.,, W. F. Wade,, and R. K. Taylor. 2001. Evaluation of cholera vaccines formulated with toxincoregulated pilin peptide plus polymer adjuvant in mice. Infect. Immun. 69: 7695– 7702.

77. Yeo, H. J.,, S. N. Savvides,, A. B. Herr,, E. Lanka,, and G. Waksman. 2000. Crystal structure of the hexameric traffic ATPase of the Helicobacter pylori type IV secretion system. Mol. Cell 6: 1461– 1472.

78. Yonekura, K.,, S. Maki-Yonekura,, and K. Namba. 2003. Complete atomic model of the bacterial flagellar filament by electron cryomicroscopy. Nature 424: 643– 650.