The RNAs and Proteins of dsRNA Viruses


Edited by Peter. P. C. Mertens, Houssam Attoui and Dennis H. Bamford

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The dsRNA genome segments and proteins of African horse sickness virus  (AHSV) 


( genus Orbivirus: family Reoviridae)


 Last updated . 20th May 2006




(Size: bp)



Protein nomenclature

(§: protein structure/




Based on data for  BTV





Based on data for


Number of Amino acids



[38, 39]

Accession numbers


Properties and Functions


Based on data for BTV




VP1 (Pol)

within the sub-core

[18, 25] at the 5 fold axis

[8, 11, 37]







RNA dependent RNA polymerase ( §: Pol) [ 41, 46, 51]





outer capsid

[19, 29]



[15, 44]



Trimer [15], controls virus serotype, serotype specific antigen [6, 19, 32, 33, 39], cell attachment protein [17, 29, 30], outer layer of the outer capsid [15, 19, 29, 39], contains neutralising epitopes [17, 30], most variable protein [32, 38, 39], involved in determination of virulence [35] cleaved by proteases [19, 29, 30].




VP3 (T2)


capsid layer


(T=2 symmetry [11])





Innermost protein capsid shell, sub-core capsid layer [11, 12, 18, 25, 26], T=2 symmetry (§: T2) [11], self assembles [34], retains icosahedral symmetry by itself [18, 25, 34], controls size and organisation of capsid structure [8,11], RNA binding [25, 26], interacts with internal minor proteins [8, 11, 18]. Highly conserved protein. Physical organisation of genome [8, 44]




VP4 (Cap)

within the sub-core [18]

at the 5 fold axis

[8, 11, 37]


20 [44]

642 D14402

Dimers [7], capping enzyme (§: Cap), guanylyltransferase [7, 24, 31], transmethylase 1 [31, 7], transmethylase 2 [31, 7].




NS1 (TuP)


forms tubules

[14, 16]


(Abundant in cell cytoplasm [16])

548 U01069

Forms tubules of unknown function [14,16] in the cell cytoplasm. These tubules are a characteristic of orbivirus replication.





outer capsid


360 [15, 44]





Inner layer of the outer capsid [15, 19, 29], glycosylated [50], helps control virus serotype [6, 32, 33], variable protein [32, 39], trimer [43, 44, 53], causes membrane fusion indicating a role in membrane penetration during initiation of infection [53].




VP6 (Hel)

Within the sub-core [18] at the 5 fold axis [8]

72 [44]





ssRNA and ds RNA binding [40], helicase [42], NTPase [42] .




VP7 (T13)

Outer core

(T=13 symmetry)

[10, 11, 12, 37]


[3, 10, 11, 12, 37]




Trimer [1, 10, 11], forms outer core surface [1, 13, 37], T=13 symmetry (§: T13)[12, 13], in some species (AHSV) it can form flat hexagonal crystals made up of layers of hexameric rings of trimers [4], involved in cell entry [30, 49], involved in high core infectivity in vector insect and cells [30, 49], reacts with "core neutralising" antibodies [30], Immuno dominant major serogroup specific antigen [5, 13, 19, 39].




NS2 (ViP)

Cytoplasm, viral inclusion bodies (VIB) [2, 45 ]


can be associated with outer capsid [29]

365 M69090

Important viral inclusion body matrix protein [2, 45], ssRNA binding [19, 20 45], phosphorylated by ubiquitous cellular kinase [20, 45, 54]. RNA binding may be affected by phosphorylation state. [54] May be associated with outer capsid [29].








Cell Membranes [21]


(Not abundant in mammalian cells) [28]





Glycoproteins [48, 52], membrane proteins [21, 52], involved in cell exit [22, 27], in some genera (AHSV) these are variable proteins [27] and may be involved in determination of virulence[35] . Cytotoxic, can disrupt cell membranes


*: Based on the genome segments of AHSV-9

**:  Based on he genome segments of AHSV-4

*** : Based on he genome segments of AHSV-6

****:  Based on ratios of the structural proteins as estimated Huismans and Van Dijk 20, 47] ,which have been normalised to 780 copies of VP7 (T13) per particle [11, 12]].


Protein numbers per particle that have been confirmed by analysis of particle atomic structure for BTV are shown in bold underlined.


†Based on the genome segment nomenclature proposed by Gorman et al [9] .


§: Protein structure / function, to facilitate identification and comparisons of proteins across species, genera and families of dsRNA viruses, as suggested by Juuti et al [23], Grimes et al [11] and Gouet et al [8] : Pol= RNA polymerase; Cap= capping enzyme (guanylyltransferase); Hel = helicase enzyme [42]; T2= protein with T=2 symmetry; T13 = Protein with T=13 symmetry; ViP= viral inclusion body matrix protein; TuP= tubule protein.


BTV = Bluetongue virus.




1. Basak, A. J., Grimes, J. M., Gouet, P., Roy, P. and Stuart, D. I. (1997) Structures of orbivirus VP7: implications for the role of this protein in the viral life cycle. Structure 5, 871-883


2. Brookes, S. M. , Hyatt, A. D. & Eaton, B. T. (1993) Characterization of virus inclusion bodies in bluetongue virus-infected cells. J. Gen. Virol. 74, 525-530.


3. Burroughs, J. N., Grimes, J. M., Mertens, P. P. C. and Stuart, D. I. (1995). Crystallisation and preliminary x-ray analysis of the core particle of bluetongue virus type 1 (South Africa). Virology 210, 217-220.


4. Burroughs, J. N., O'Hara, R. S., Smale, C. J., Hamblin, C., Walton, A., Armstrong, R. and Mertens, P. P. C. (1994) Purification and properties of virus particles, infectious sub viral particles, cores and VP7 crystals of African Horse sickness virus serotype 9. Journal of General Virology 75:1849-1857.


5. Collen, T., Mertens, P. P. C., Burroughs, J. N., Butcher, R. N., Anderson, J., Windsor, M. and Takamatsu, H. (1992). Monoclonal antibodies produced against bluetongue and African horse sickness viruses by in vitro immunization show a bias for structural protein VP7. Bluetongue, African horse sickness and related orbiviruses: Proceedings of the Second International Symposium, Paris, 17-21 June 1991 edited by WALTON T. E. & OSBURN B. I. Boca Raton: CRC Press, 416-422.


6. Cowley, J. A., and Gorman, B. M. (1989) Cross-neutralisation of genetic reassortants of bluetongue virus serotypes 20 and 21. Veterinary Microbiology 19, 37-51


7. Devi, R., Burroughs, J. N., Mertens, P. P. C, and Roy, P. Transmethylase 1 and Transmethylase 2 activities associated with the Cap protein (VP4) of BTV, in native cores, core like particles and as a purified, baculovirus expressed protein. (Proc. Natl. Acad. Sci. USA, in press).


8. Gouet, P., Grimes, J. M., Diprose, J. M., Malby, R., Zientara, S., Burroughs, J. N., Stuart D. I. and Mertens, P. P. C. Crystallographic studies show ordered double-stranded RNA in bluetongue virus (letter, in preparation for submission to Nature).


9. Gorman, B. M., Ghaleb, H. W., Huismans, H., Joklik, W. K., Knudson D. L., McPhee, D. A. Murphy, F. A., Ritchie, A., Roy, P., and Taylor J., (1985)WHO/FAO working team report: molecular virology. In "Bluetongue and Related orbiviruses" (Eds. T. Barber & M. M. Jochim) Alan R. Liss: New York pp 689-695.


10. Grimes, J. M., Basak, A. J., Roy, P. and Stuart, D. I. (1995) the crystal structure of bluetongue virus VP7. Nature 373, 167-170.


11. Grimes, J. M., Burroughs, J. N., Gouet, P., Diprose, J. M., Malby, R., Zientara, S., Mertens, P. P. C. and Stuart D. I. The atomic structure of the bluetongue virus core (Nature in press).


12. Grimes, J. M., Jakan, J., Ghosh, M., Basak, A. J., Roy, P., Chiu, W., Stuart, D. I. and Prasad, B. V. V. (1997) An atomic model of the outer layer of the bluetongue virus core derived from x-ray crystallography and electron cryomicroscopy, Structure 5, 885-893.


13. Gumm I. D., and Newman, J. F. E. (1982) the preparation of purified bluetongue virus group antigen for use as a diagnostic reagent. Archives of Virology 72, 83-89.


14. Hewat, E. A., Booth, T. F., Wade, R. H. And Roy, P. (1992) 3-D reconstruction of bluetongue virus tubules using cryo electron microscopy. Journal of Structural Biology 108, 35-48.


15. Hewat, E. A., Booth, T. F. and Roy, P. (1992) Structure of bluetongue virus particles by cryo electron microscopy. Journal of Structural Biology 10, 61-69.


16. Huismans, H. and Els, H. J. (1979) Characterization of tubules associated with the replication of the different orbiviruses. Virology 92, 397-406.


17. Huismans, H., Van Der Walt, N. T., Cloete, M., and Erasmus, B. J. (1987) Isolation of a capsid protein of bluetongue virus that induces a protective immune response in sheep. Virology 61, 3589-3595.


18. Huismans, H., Van Dijk, A. A. & Els, J. H. (1987). Uncoating of parental bluetongue virus to core and subcore particles in infected L cells. Virology 157, 180-188.


19. Huismans, H. and Van Dijk, A. A. (1990) Bluetongue virus structural components. Current Topics in Microbiology and Immunology 162, 21-42.


20. Huismans, H. Van Dijk, A. A. and Bauskin, A. R., In Vitro phosphorylation and purification of nonstructural protein of bluetongue virus with affinity for single stranded RNA. J. Virol. 61, 3589-3595).


21. Hyatt, A. D., Gould A. R., Coupar, B. and Eaton, B. T. (1991) localisation of the non-structural protein NS3 in bluetongue infected cells. Journal of General Virology 72, 2263-2267.


22. Hyatt, A. D., Zhao, Y. & Roy, P. (1993) release of bluetongue virus-like particles from insect cells is mediated by BTV non-structural protein NS3/3a. Virology 193, 592-603.


23. Juuti, J.T., Ravantti, J.J., Bamford, D.H. (1997) The Common and uncommon amoung dsRNA viruses. in "6th International Symposium on dsRNA Viruses" (Cocoyoc, Mexico) (eds. Arias CF, Lopez S) pp A1-A10.


24. Le Blois, H., French, T., Mertens, P. P. C., Burroughs, J. N. and Roy, P. (1992) The expressed VP4 protein of bluetongue virus binds GTP and is the candidate guanylyl transferase of the virus. Virology 189, 757-761.


25. Loudon, P. T. & Roy, P. (1991) Assembly of five bluetongue virus proteins expressed by recombinant baculoviruses: inclusion of the largest protein VP1 in the core and virus like particles. Virology 180, 798-802.


26. Loudon, P. T., and Roy, P. (1992) Interaction of nucleic acids with core-like and subcore-like particles of bluetongue virus. Virology 191, 231-236.


27. Martin, L.-A., Meyer, A. J., O'Hara, R. S., Fu, H., Knowles, N. J. and Mertens P. P. C. (1998) Phylogenetic analysis of African horse sickness virus genome segment 10: sequence variation and virulence characteristics Archives of Virology supplement 14 (in Press).


28. Mertens, P. P. C., Brown, F. & Sangar, D. V. (1984). Assignment of the genome segments of bluetongue virus type 1 to the proteins which they encode. Virology 135, 207-217.


29. Mertens, P. P. C., Burroughs, J. N. & Anderson, J. (1987) Purification and properties of virus particles, infectious subviral particles, and cores of bluetongue virus serotype 1 and 4. Virology 157, 375-386.


30. Mertens, P. P. C., Burroughs, J. N., Walton, A., Welby, M. P., Fu, H., O'Hara, R. S., Brookes, S. M. & Mellor, P. S. (1995). Enhanced infectivities of modified bluetongue virus for two insect cell lines for two Culicoides vector species. Virology 217, 582-593.


31. Mertens, P. P. C., Burroughs, J. N., Wade-Evans, A. M., Le Blois, H., Oldfield, S., Basak, A., Loudon, P. & Roy, P. (1992). Analysis of guanylyltransferase and transmethylase activities associated with bluetongue virus cores and recombinant baculovirus-expressed core-like particles. Bluetongue, African horse sickness and related orbiviruses: Proceedings of the Second International Symposium, Paris, 17-21 June 1991 edited by WALTON T. E. & OSBURN B. I. Boca Raton: CRC Press, 404-415.


32. Mertens, P. P. C., Pedley, S., Cowley, J. and Burroughs, J. N. (1987). A comparison of six different bluetongue virus isolates by crosshybridisation of the dsRNA genome segments. Virology, 161:438-447.


33. Mertens, P. P. C., Pedley, S., Cowley, J., Burroughs, J. N., Corteyn, A. H., Jeggo, M. H., Jennings, A. M. and Gorman, B. M. (1989). Analysis of the roles of bluetongue virus outer capsid proteins VP2 and VP5 in determination of virus serotype. Virology 170,561-565.


34. Moss, S. R. & Nuttall, P.A. (1994) Subcore and core-like particles of Broadhaven virus (BRDV), a tick bourne orbivirus , synthesised from baculovirus expressed VP2 and VP7, the major core proteins of BRDV. Virus Res. 32, 401- 407.


35. O’Hara, R. S., Meyer, A. J., Pullen, L., Martin, L.-A. and Mertens, P. P. C. (1998) Development of a mouse model system and identification of individual genome segments of African horse sickness virus, serotypes 3 and 8 involved in determination of virulence: abstract. Archives of Virology Supplement 14 (in Press).


36. Pedley, S., Mohamed, M. E. H. and Mertens, P. P. C. (1988). Analysis of the genome segments of six different bluetongue virus isolates using RNA-RNA hybridisation: A generalised coding assignment for bluetongue viruses. Virus Research 10, 381-390.


37. Prasad, B. V. V., Yamaguichi, S. & Roy, P. (1992). Three-dimensional structure of single-shelled BTV. J. Virol. 66, 2135-2142.


38. Roy, P. (1989) Bluetongue virus genetics and genome structure. Virus Research 13, 179-206.


39. Roy, P. (1989) Bluetongue virus proteins. Journal of General Virology 73, 3051-3064.


40. Roy, P., Adachi , A., Urakawa, T. , Booth, T. F., and Thomas, C. P., (1990) identification of bluetongue virus VP6 as nucleic acid binding protein and the localisation of VP6 in virus infected cells Journal of Virology 64, 1-8.


41. Roy, P., Fukusho, A., Ritter D. G. and Lyons D. (1988) Evidence for genetic relationship between RNA and DNA viruses from the sequence homology of a putative polymerase gene of bluetongue virus with that of vaccinia virus : conservation of RNA polymerase genes from diverse species. Nucleic Acids Research 16, 11759-11767.


42. Stauber, N., Martinez-Costas, J., Sutton, G., Monastyrskaya, K. and Roy, P. (1997) Bluetongue virus VP6 protein binds ATP and exhibits an RNA-dependent ATPase function and a helicase activity that catalyze the unwinding of double-stranded RNA substrates. Journal of Virology 71, 7220-7226.


43. Schoehn, G., Moss, S. R., Nuttall, P. A. and Hewat, E. A. (1997) Structure of Broadhaven virus by cryo electron microscopy: correlation of structural and antigenic properties of Broadhaven virus and bluetongue virus outer capsid proteins. Virology 235, 191-200.


44. Stuart, D., Gouet, P., Grimes, J., Malby, R., Diprose, J., Zientara, S., Burroughs, J. N., Wade-Evans, A. M. and Mertens, P. P. C. (1998) Structural studies of orbivirus particles: Archives of Virology, supplement 14 (in Press).


45. Thomas, C. P. Booth, T. F., and Roy, P. (1990) Synthesis of bluetongue virus encoded phosphoprotein , and formation of inclusion bodies by recombinant baculovirus in insect cells : it binds the single stranded RNA species. Journal of Gen Virol 71, 2073-2083.


46. Urakawa, T., Ritter, D. G., and Roy, P. (1989) Expression of the largest RNA segment and synthesis of VP1 protein of bluetongue virus in insect cells by recombinant baculovirus : association of VP1 protein with RNA polymerase activity. Nucleic Acids Research 17, 7395-7401.


47. Verwoerd, D. W., Els, H. J., DE Villers, E. M. & Huismans, H. (1972). Structure of the bluetongue virus capsid. Journal of Virology. 10, 783-794.


48. Wu, X. Chen, S-y. Iwata, H. Compans, R. W. And Roy P.(1992) Multiple glycoproteins synthesized by the smallest RNA segment (S10) of bluetongue virus. Journal of Virology 66,7104-7112.


49. Xu, G., Wilson, W., Mecham, J., Murphy, K., Zhou, E-M. and Tabachnick W. (1997) VP7: an attachment protein of bluetongue virus for cellular receptors in Culicoides variipennis. Journal of General Virology 78 , 1617-1623.


50. Yang, Y-Y. Li, J. K. K (1993) Glycosylation of the major outer capsid protein of bluetongue viruses. Virology 194,350-354.


51. Boyce M. Wehrfritz J. Noad R. Roy P. Purified recombinant bluetongue virus VP1 exhibits RNA replicase activity. Journal of Virology 2004 78  3994-4002.


52. Bansal OB, Stokes A, Bansal A, Bishop D, Roy P.(1998) Membrane organization of bluetongue virus nonstructural glycoprotein NS3. Journal of Virology. 72, :3362-3369.


53. Hassan SH, Wirblich C, Forzan M, Roy P. (2001)  Expression and functional characterization of bluetongue virus VP5 protein: role in cellular permeabilization. Journal of Virology 75, 8356-67.


54 Theron, J., Uitenweerde, J.M., Huismans, H. and Nel, L. H. (1994) Comparison of the expression and phosphorylation of the non-structural protein NS2 of three different orbiviruses: evidence for the involvement of an ubiquitous cellular kinase. Journal of General Virology. Dec;75 ( Pt 12): 3401-3411.



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(The RNAs and Proteins  of dsRNA Viruses:  Edited by Peter. P. C. Mertens, Houssam Attoui and Dennis H. Bamford)