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Structural basis for membrane anchoring and fusion regulation of the herpes simplex virus fusogen gB

Nature Structural & Molecular Biologyvolume 25pages416424 (2018) | Download Citation


Viral fusogens merge viral and cell membranes during cell penetration. Their ectodomains drive fusion by undergoing large-scale refolding, but little is known about the functionally important regions located within or near the membrane. Here we report the crystal structure of full-length glycoprotein B (gB), the fusogen from herpes simplex virus, complemented by electron spin resonance measurements. The membrane-proximal (MPR), transmembrane (TMD), and cytoplasmic (CTD) domains form a uniquely folded trimeric pedestal beneath the ectodomain, which balances dynamic flexibility with extensive, stabilizing membrane interactions. The postfusion conformation of the ectodomain suggests that the CTD likewise adopted the postfusion form. However, hyperfusogenic mutations, which destabilize the prefusion state of gB, target key interfaces and structural motifs that reinforce the observed CTD structure. Thus, a similar CTD structure must stabilize gB in its prefusion state. Our data suggest a model for how this dynamic, membrane-dependent ‘clamp’ controls the fusogenic refolding of gB.

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  1. 1.

    Kennedy, P. G. & Steiner, I. Recent issues in herpes simplex encephalitis. J. Neurovirol. 19, 346–350 (2013).

  2. 2.

    Rowe, A. M. et al. Herpes keratitis. Prog. Retin. Eye Res. 32, 88–101 (2013).

  3. 3.

    Santos, C. A. Cytomegalovirus and other β-herpesviruses. Semin. Nephrol. 36, 351–361 (2016).

  4. 4.

    Britt, W. J. Congenital human cytomegalovirus infection and the enigma of maternal immunity. J. Virol. 91, e02392 (2017).

  5. 5.

    Young, L. S., Yap, L. F. & Murray, P. G. Epstein–Barr virus: more than 50 years old and still providing surprises. Nat. Rev. Cancer 16, 789–802 (2016).

  6. 6.

    Eisenberg, R. J. et al. Herpes virus fusion and entry: a story with many characters. Viruses 4, 800–832 (2012).

  7. 7.

    Sathiyamoorthy, K., Chen, J., Longnecker, R. & Jardetzky, T. S. The COMPLEXity in herpesvirus entry. Curr. Opin. Virol. 24, 97–104 (2017).

  8. 8.

    Harrison, S. C. Viral membrane fusion. Virology 479–480C, 498–507 (2015).

  9. 9.

    Heldwein, E. E. et al. Crystal structure of glycoprotein B from herpes simplex virus 1. Science 313, 217–220 (2006).

  10. 10.

    Backovic, M., Longnecker, R. & Jardetzky, T. S. Structure of a trimeric variant of the Epstein–Barr virus glycoprotein B. Proc. Natl Acad. Sci. USA 106, 2880–2885 (2009).

  11. 11.

    Burke, H. G. & Heldwein, E. E. Crystal structure of the human cytomegalovirus glycoprotein B. PLoS Pathog. 11, e1005227 (2015).

  12. 12.

    Chandramouli, S. et al. Structure of HCMV glycoprotein B in the postfusion conformation bound to a neutralizing human antibody. Nat. Commun. 6, 8176 (2015).

  13. 13.

    Jones, N. A. & Geraghty, R. J. Fusion activity of lipid-anchored envelope glycoproteins of herpes simplex virus type 1. Virology 324, 213–228 (2004).

  14. 14.

    Fan, Z. et al. Truncation of herpes simplex virus type 2 glycoprotein B increases its cell surface expression and activity in cell–cell fusion, but these properties are unrelated. J. Virol. 76, 9271–9283 (2002).

  15. 15.

    Wanas, E., Efler, S., Ghosh, K. & Ghosh, H. P. Mutations in the conserved carboxy-terminal hydrophobic region of glycoprotein gB affect infectivity of herpes simplex virus. J. Gen. Virol. 80, 3189–3198 (1999).

  16. 16.

    Lin, E. & Spear, P. G. Random linker-insertion mutagenesis to identify functional domains of herpes simplex virus type 1 glycoprotein B. Proc. Natl Acad. Sci. USA 104, 13140–13145 (2007).

  17. 17.

    Gage, P. J., Levine, M. & Glorioso, J. C. Syncytium-inducing mutations localize to two discrete regions within the cytoplasmic domain of herpes simplex virus type 1 glycoprotein B. J. Virol. 67, 2191–2201 (1993).

  18. 18.

    Baghian, A., Huang, L., Newman, S., Jayachandra, S. & Kousoulas, K. G. Truncation of the carboxy-terminal 28 amino acids of glycoprotein B specified by herpes simplex virus type 1 mutant amb1511-7 causes extensive cell fusion. J. Virol. 67, 2396–2401 (1993).

  19. 19.

    Chowdary, T. K. & Heldwein, E. E. Syncytial phenotype of C-terminally truncated herpes simplex virus type 1 gB is associated with diminished membrane interactions. J. Virol. 84, 4923–4935 (2010).

  20. 20.

    Zoonens, M. & Popot, J. L. Amphipols for each season. J. Membr. Biol. 247, 759–796 (2014).

  21. 21.

    Zheng, Z., Maidji, E., Tugizov, S. & Pereira, L. Mutations in the carboxyl-terminal hydrophobic sequence of human cytomegalovirus glycoprotein B alter transport and protein chaperone binding. J. Virol. 70, 8029–8040 (1996).

  22. 22.

    Rogalin, H. B. & Heldwein, E. E. The interplay between the HSV-1 gB cytodomains and the gH cytotail during cell–cell fusion. J. Virol. 89, 12262–12272 (2015).

  23. 23.

    Langelaan, D. N., Wieczorek, M., Blouin, C. & Rainey, J. K. Improved helix and kink characterization in membrane proteins allows evaluation of kink sequence predictors. J. Chem. Inf. Model. 50, 2213–2220 (2010).

  24. 24.

    Hannah, B. P. et al. Herpes simplex virus glycoprotein B associates with target membranes via its fusion loops. J. Virol. 83, 6825–6836 (2009).

  25. 25.

    Ruel, N., Zago, A. & Spear, P. G. Alanine substitution of conserved residues in the cytoplasmic tail of herpes simplex virus gB can enhance or abolish cell fusion activity and viral entry. Virology 346, 229–237 (2006).

  26. 26.

    Silverman, J. L., Greene, N. G., King, D. S. & Heldwein, E. E. Membrane requirement for folding of the herpes simplex virus 1 gB cytodomain suggests a unique mechanism of fusion regulation. J. Virol. 86, 8171–8184 (2012).

  27. 27.

    Mchaourab, H. S., Lietzow, M. A., Hideg, K. & Hubbell, W. L. Motion of spin-labeled side chains in T4 lysozyme. Correlation with protein structure and dynamics. Biochemistry 35, 7692–7704 (1996).

  28. 28.

    Haffar, O. K., Dowbenko, D. J. & Berman, P. W. The cytoplasmic tail of HIV-1 gp160 contains regions that associate with cellular membranes. Virology 180, 439–441 (1991).

  29. 29.

    Lai, A. L., Park, H., White, J. M. & Tamm, L. K. Fusion peptide of influenza hemagglutinin requires a fixed angle boomerang structure for activity. J. Biol. Chem. 281, 5760–5770 (2006).

  30. 30.

    Stoll, S. et al. Double electron–electron resonance shows cytochrome P450cam undergoes a conformational change in solution upon binding substrate. Proc. Natl Acad. Sci. USA 109, 12888–12893 (2012).

  31. 31.

    Zou, P., Bortolus, M. & McHaourab, H. S. Conformational cycle of the ABC transporter MsbA in liposomes: detailed analysis using double electron–electron resonance spectroscopy. J. Mol. Biol. 393, 586–597 (2009).

  32. 32.

    Walev, I., Lingen, M., Lazzaro, M., Weise, K. & Falke, D. Cyclosporin A resistance of herpes simplex virus–induced “fusion from within” as a phenotypical marker of mutations in the Syn 3 locus of the glycoprotein B gene. Virus Genes 8, 83–86 (1994).

  33. 33.

    Muggeridge, M. I. Characterization of cell–cell fusion mediated by herpes simplex virus 2 glycoproteins gB, gD, gH and gL in transfected cells. J. Gen. Virol. 81, 2017–2027 (2000).

  34. 34.

    Cai, W. H., Gu, B. & Person, S. Role of glycoprotein B of herpes simplex virus type 1 in viral entry and cell fusion. J. Virol. 62, 2596–2604 (1988).

  35. 35.

    Engel, J. P., Boyer, E. P. & Goodman, J. L. Two novel single amino acid syncytial mutations in the carboxy terminus of glycoprotein B of herpes simplex virus type 1 confer a unique pathogenic phenotype. Virology 192, 112–120 (1993).

  36. 36.

    Diakidi-Kosta, A., Michailidou, G., Kontogounis, G., Sivropoulou, A. & Arsenakis, M. A single amino acid substitution in the cytoplasmic tail of the glycoprotein B of herpes simplex virus 1 affects both syncytium formation and binding to intracellular heparan sulfate. Virus Res. 93, 99–108 (2003).

  37. 37.

    Muggeridge, M. I., Grantham, M. L. & Johnson, F. B. Identification of syncytial mutations in a clinical isolate of herpes simplex virus 2. Virology 328, 244–253 (2004).

  38. 38.

    Bzik, D. J., Fox, B. A., DeLuca, N. A. & Person, S. Nucleotide sequence of a region of the herpes simplex virus type 1 gB glycoprotein gene: mutations affecting rate of virus entry and cell fusion. Virology 137, 185–190 (1984).

  39. 39.

    Foster, T. P., Melancon, J. M. & Kousoulas, K. G. An α-helical domain within the carboxyl terminus of herpes simplex virus type 1 (HSV-1) glycoprotein B (gB) is associated with cell fusion and resistance to heparin inhibition of cell fusion. Virology 287, 18–29 (2001).

  40. 40.

    Chen, J., Zhang, X., Jardetzky, T. S. & Longnecker, R. The Epstein–Barr virus (EBV) glycoprotein B cytoplasmic C-terminal tail domain regulates the energy requirement for EBV-induced membrane fusion. J. Virol. 88, 11686–11695 (2014).

  41. 41.

    Garcia, N. J., Chen, J. & Longnecker, R. Modulation of Epstein–Barr virus glycoprotein B (gB) fusion activity by the gB cytoplasmic tail domain. MBio 4, e00571–12 (2013).

  42. 42.

    Haan, K. M., Lee, S. K. & Longnecker, R. Different functional domains in the cytoplasmic tail of glycoprotein B are involved in Epstein–Barr virus–induced membrane fusion. Virology 290, 106–114 (2001).

  43. 43.

    Postler, T. S. & Desrosiers, R. C. The tale of the long tail: the cytoplasmic domain of HIV-1 gp41. J. Virol. 87, 2–15 (2013).

  44. 44.

    Haanes, E. J., Nelson, C. M., Soule, C. L. & Goodman, J. L. The UL45 gene product is required for herpes simplex virus type 1 glycoprotein B–induced fusion. J. Virol. 68, 5825–5834 (1994).

  45. 45.

    Chen, J. et al. HIV-1 ENVELOPE. Effect of the cytoplasmic domain on antigenic characteristics of HIV-1 envelope glycoprotein. Science 349, 191–195 (2015).

  46. 46.

    Dev, J. et al. Structural basis for membrane anchoring of HIV-1 envelope spike. Science 353, 172–175 (2016).

  47. 47.

    Kemble, G. W., Danieli, T. & White, J. M. Lipid-anchored influenza hemagglutinin promotes hemifusion, not complete fusion. Cell 76, 383–391 (1994).

  48. 48.

    Nixdorf, R., Klupp, B. G., Karger, A. & Mettenleiter, T. C. Effects of truncation of the carboxy terminus of pseudorabies virus glycoprotein B on infectivity. J. Virol. 74, 7137–7145 (2000).

  49. 49.

    Waning, D. L., Russell, C. J., Jardetzky, T. S. & Lamb, R. A. Activation of a paramyxovirus fusion protein is modulated by inside-out signaling from the cytoplasmic tail. Proc. Natl Acad. Sci. USA 101, 9217–9222 (2004).

  50. 50.

    Sun, Z. Y. et al. Disruption of helix-capping residues 671 and 674 reveals a role in HIV-1 entry for a specialized hinge segment of the membrane proximal external region of gp41. J. Mol. Biol. 426, 1095–1108 (2014).

  51. 51.

    Zhang, X. et al. Cryo-EM structure of the mature dengue virus at 3.5-Å resolution. Nat. Struct. Mol. Biol. 20, 105–110 (2013).

  52. 52.

    Sirohi, D. et al. The 3.8 Å resolution cryo-EM structure of Zika virus. Science 352, 467–470 (2016).

  53. 53.

    Vitu, E., Sharma, S., Stampfer, S. D. & Heldwein, E. E. Extensive mutagenesis of the HSV-1 gB ectodomain reveals remarkable stability of its postfusion form. J. Mol. Biol. 425, 2056–2071 (2013).

  54. 54.

    Patrone, M. et al. Enhanced expression of full-length human cytomegalovirus fusion protein in non-swelling baculovirus-infected cells with a minimal fed-batch strategy. PLoS One 9, e90753 (2014).

  55. 55.

    Zeev-Ben-Mordehai, T. et al. Two distinct trimeric conformations of natively membrane-anchored full-length herpes simplex virus 1 glycoprotein B. Proc. Natl Acad. Sci. USA 113, 4176–4181 (2016).

  56. 56.

    Fontana, J. et al. The fusion loops of the initial prefusion conformation of herpes simplex virus 1 fusion protein point toward the membrane. MBio 8, e01268–17 (2017).

  57. 57.

    Harman, A., Browne, H. & Minson, T. The transmembrane domain and cytoplasmic tail of herpes simplex virus type 1 glycoprotein H play a role in membrane fusion. J. Virol. 76, 10708–10716 (2002).

  58. 58.

    Browne, H. M., Bruun, B. C. & Minson, A. C. Characterization of herpes simplex virus type 1 recombinants with mutations in the cytoplasmic tail of glycoprotein H. J. Gen. Virol. 77, 2569–2573 (1996).

  59. 59.

    Morin, A. et al. Collaboration gets the most out of software. eLife 2, e01456 (2013).

  60. 60.

    Charvolin, D., Picard, M., Huang, L. S., Berry, E. A. & Popot, J. L. Solution behavior and crystallization of cytochrome bc 1 in the presence of amphipols. J. Membr. Biol. 247, 981–996 (2014).

  61. 61.

    Kabsch, W. Xds. Acta Crystallogr. D Biol. Crystallogr. 66, 125–132 (2010).

  62. 62.

    McCoy, A. J. et al. Phaser crystallographic software. J. Appl. Crystallogr. 40, 658–674 (2007).

  63. 63.

    Emsley, P., Lohkamp, B., Scott, W. G. & Cowtan, K. Features and development of Coot. Acta Crystallogr. D Biol. Crystallogr. 66, 486–501 (2010).

  64. 64.

    Adams, P. D. et al. PHENIX: a comprehensive Python-based system for macromolecular structure solution. Acta Crystallogr. D Biol. Crystallogr. 66, 213–221 (2010).

  65. 65.

    Gouet, P., Courcelle, E., Stuart, D. I. & Métoz, F. ESPript: analysis of multiple sequence alignments in PostScript. Bioinformatics 15, 305–308 (1999).

  66. 66.

    Collaborative Computational Project, Number 4. The CCP4 suite: programs for protein crystallography. Acta Crystallogr. D Biol. Crystallogr. 50, 760–763 (1994).

  67. 67.

    Georgieva, E. R., Xiao, S., Borbat, P. P., Freed, J. H. & Eliezer, D. Tau binds to lipid membrane surfaces via short amphipathic helices located in its microtubule-binding repeats. Biophys. J. 107, 1441–1452 (2014).

  68. 68.

    Zou, P. & McHaourab, H. S. Alternating access of the putative substrate-binding chamber in the ABC transporter MsbA. J. Mol. Biol. 393, 574–585 (2009).

  69. 69.

    Pannier, M., Veit, S., Godt, A., Jeschke, G. & Spiess, H. W. Dead-time free measurement of dipole–dipole interactions between electron spins. J. Magn. Reson. 142, 331–340 (2000).

  70. 70.

    Borbat, P. P., Crepeau, R. H. & Freed, J. H. Multifrequency two-dimensional Fourier transform ESR: an X/Ku-band spectrometer. J. Magn. Reson. 127, 155–167 (1997).

  71. 71.

    Chiang, Y. W., Borbat, P. P. & Freed, J. H. The determination of pair distance distributions by pulsed ESR using Tikhonov regularization. J. Magn. Reson. 172, 279–295 (2005).

  72. 72.

    Chiang, Y. W., Borbat, P. P. & Freed, J. H. Maximum entropy: a complement to Tikhonov regularization for determination of pair distance distributions by pulsed ESR. J. Magn. Reson. 177, 184–196 (2005).

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We thank NE-CAT staff for help with X-ray data collection and H. Rogalin for help with the cell–cell fusion assay. We also thank P. G. Spear (Northwestern University), R. J. Eisenberg (University of Pennsylvania), and G. H. Cohen (University of Pennsylvania) for the gift of plasmids and J. M. Coffin (Tufts University) for the gift of CHO cells. This work was funded by NIH grant 1R21AI107171 (E.E.H.), the Burroughs Wellcome Fund (E.E.H.), and the NIH Ruth L. Kirschstein NRSA postdoctoral fellowship 1F32GM115060 (R.S.C.). The research of E.E.H. was supported in part by a Faculty Scholar grant from the Howard Hughes Medical Institute. ESR experiments were funded by NIH grants P41GM103521 (J.H.F., ACERT) and R01GM123779 (J.H.F. and E.R.G.). This work is based upon research conducted at the Northeastern Collaborative Access Team beamlines, which are funded by the National Institute of General Medical Sciences from the NIH (P41GM103403). The Pilatus 6 M detector on the 24-ID-C beamline is funded by an NIH-ORIP HEI grant (S10RR029205). This research used resources of the Advanced Photon Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under contract DE-AC02-06CH11357. All software was installed and maintained by SBGrid59.

Author information


  1. Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA, USA

    • Rebecca S. Cooper
    •  & Ekaterina E. Heldwein
  2. Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, USA

    • Elka R. Georgieva
    • , Peter P. Borbat
    •  & Jack H. Freed
  3. National Biomedical Center for Advanced Electron Spin Resonance Technology (ACERT), Cornell University, Ithaca, NY, USA

    • Elka R. Georgieva
    • , Peter P. Borbat
    •  & Jack H. Freed


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R.S.C. designed experiments, cloned the constructs, produced recombinant proteins, crystallized gBdelta71, collected diffraction data, phased the data and determined the structure, built and refined the models, carried out cell-cell fusion assays, analyzed the data, and wrote the manuscript. E.R.G. designed ESR studies, carried out spin labeling and lipid reconstitution, collected, analyzed, and interpreted ESR data, and wrote the manuscript. P.P.B. collected, analyzed, and interpreted ESR data, and wrote the manuscript. J.H.F. wrote the manuscript. E.E.H. designed experiments, phased the data and determined the structure, built and refined the models, analyzed the data, and wrote the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Ekaterina E. Heldwein.

Integrated supplementary information

  1. Supplementary Figure 1 Purification and crystallization of gBd71.

    a, SEC of gBΔ71 in 0.05% n-dodecyl-β-d-maltopyranoside (DDM) reveals a trimer with an apparent molecular weight of 415 kDa. b, SDS–PAGE analysis of the peak SEC fractions, separated from aggregated protein. c, Representative H32 crystals of gBΔ71 in 0.075% n-undecyl-β-d-maltopyranoside and 0.0075% A8-35 amphipol. d, Representative P321 gBΔ71 crystals in 0.05% n-dodecyl-β-d-maltopyranoside and 0.01% A8-35 amphipol. e, gBΔ71 packing within P321 crystals. The folded CTD core (blue) packs against the crown of the trimer below (orange), an interaction that presumably stabilizes both the CTD and TMD.

  2. Supplementary Figure 2 Residue conservation in human herpesviruses.

    a, Sequence alignment of eight human herpesviruses, with identical residues boxed in magenta and similar residues boxed in gray. Residues that contribute to potentially important HSV-1 CTD features, including its acidic face and membrane-binding basic belt, are indicated with stars. Nearby basic residues that may perform a similar function in other herpesviruses are boxed. The regions resolved in the crystal structure and by ESR are underlined in orange and green, respectively. Secondary structure elements are shown above the alignment. b,c, Top and side views of the MPR–TMD–CTD pedestal, with protomers shown in different shades of blue. Identical residues in the alignment are shown as magenta spheres. d, A close-up view of the TMD–h1a–h1b zigzag.

  3. Supplementary Figure 3 Residue conservation in α-herpesviruses.

    a, Sequence alignment of 13 α-herpesviruses. Residues that contribute to important HSV-1 CTD features, including its membrane-binding basic belt and acidic face, are indicated with stars. Nearby basic residues that may perform a similar function in other herpesviruses are boxed. b, Residues identical in these viruses, as well as among eight human herpesviruses from different subfamilies, are mapped onto side and top views of the MPR–TMD–CTD.

  4. Supplementary Figure 4 Effect of the ordered CTD on TMD and MPR.

    a, The well-ordered CTD of FL-gB (P321 crystals) packs against the crown of the trimer below (Supplementary Fig. 1e), which appears to stabilize the position of the TMD helices. b, When the CTD of FL-gB is disordered (H32 crystals), the C terminus of the TMD is unresolved and both the MPR–TMD and TMD–TMD angles increase.

  5. Supplementary Figure 5 Interprotomer interactions in the CTD.

    Four classes of interactions were identified using CCP4 Contact. Only interactions ≤ 4 Å are depicted for simplicity. The “van der Waals + mixed” category indicates that a pair of residues may be linked by either van der Waals interactions or a combination of hydrophobic and van der Waals interactions. Positions where mutations alter the rate of fusion are shaded. Bolded residues are conserved in α-herpesviruses. Box colors indicate hyperfusogenic mutations identified in clinical isolates (light orange) or engineered (light green) as well as a single slow-entry mutation (light blue). Box outline colors indicate whether the collective interactions of a residue are mediated by main chain atoms (red), side chain atoms (blue), or both (purple).

  6. Supplementary Figure 6 Fusion activity of single-cysteine FL-gB mutants.

    Cell–cell fusion between effector cells expressing gD, gH–gL, and single-cysteine gB mutants and target cells expressing gD receptor HVEM was tested using a luciferase assay. The previously identified hyperfusogenic mutant R858H was included as a control for each assay. Every mutant was tested in at least two biological replicates (n), each consisting of three technical replicates. Dots show the average fusion activity of each biological replicate relative to wild-type gB (100% fusion). Depending on the background plasmid for mutant construction (indicated in the source data available online), wild-type gB denotes either pPEP98 or pRC30. Error bars show 1 s.d. from the biological replicate average, which is marked with a wider central bar. The activity of E816C was not tested. Most mutants had a wild-type or mildly hyperfusogenic phenotype, indicating that the global structure of the h2–h3 region was not significantly altered by these substitutions. For K862C, V880C, M881C, and R882C, which have hyperfusogenic phenotypes, interaction of the native side chains with the membrane may be stronger than that of the cysteine and important for CTD stability. Source data

  7. Supplementary Figure 7 Accessibility and mobility of the CTD C terminus in the presence of membrane.

    a, Accessibility (Π) of CTD residues 861–885 to 4.5 mM NiEDDA and O2. b, Mobility (1/ΔH) of CTD residues 861–885. c, The mobility of residues 876–884 follows a periodic pattern (inset) that is consistent with an amphipathic helix in which the movement of membrane-facing residues is restricted. The D878C mutant precipitated and was excluded from measurements. Measurements were collected once on each mutant, with the exception of V876C, M879C, R882C, and R884C, which were tested twice. Initial validation of the data collection protocol on these isolated mutants produced similar results, but only the complete range was used for depth calculations and subsequent analysis.

Supplementary information

  1. Supplementary Text and Figures

    Supplementary Figures 1–7, Supplementary Tables 1 and 2, and Supplementary Note

  2. Reporting Summary

  3. Supplementary Table 3

    Single-cysteine mutant cloning

  4. Source Data for Supplementary Figure 6

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