PROSITE documentation PDOC00480
Plant viruses icosahedral capsid proteins 'S' region signature


The capsid protein of plant icosahedral positive strand RNA viruses generally consists of four distinct domains: an N-terminal positively charged 'R' domain involved in the interaction with RNA, a connecting arm 'a', a central domain 'S' forming the virion shell, and a C-terminal projecting 'P' domain. Some of the viruses lack either the R or P domains.

It has been shown [1] that the S domain of the capsid protein of a number of plant viruses are evolutionary related, namely:

  • Carmoviruses: carnation mottle virus (CarMV), melon necrotic spot virus (MNSV), and turnip crinkle virus (TCV).
  • Dianthoviruses: red clover necrotic mosaic virus (RCNMV).
  • Sobemoviruses: maize chlorotic mottle virus (MCMV), and southern bean mosaic virus (SBMV).
  • Tombusviruses: artichoke mottled crinkle virus (AMCV), cucumber necrosis virus (CNV), cymbidium ringspot virus (CyRSV), and tomato bushy stunt virus (TBSV).
  • Tobacco necrosis virus (TNV).

The S domain of these viruses contains from 158 to 166 amino acids and is composed of eight β-strand anti-parallel twisted sheets in what is known as a 'jellyroll' conformation. The signature pattern for this domain starts at the C-terminal part of the 3rd β-strand and extends up to the end of the 4th strand.

Expert(s) to contact by email:

Koonin E.V.

Last update:

November 1997 / Pattern and text revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

ICOSAH_VIR_COAT_S, PS00555; Plant viruses icosahedral capsid proteins 'S' region signature  (PATTERN)


1AuthorsDolja V.V. Koonin E.V.
TitlePhylogeny of capsid proteins of small icosahedral RNA plant viruses.
SourceJ. Gen. Virol. 72:1481-1486(1991).
PubMed ID1856686

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