Notes on Genus: Alphavirus

enveloped spheres
enveloped spheres

Type member: Sindbis virus

Contents

General Description

This is one of two genera in the family Togaviridae and consists of those viruses with a genome of 11-12kb that encodes four structural proteins (coat protein and three membrane proteins). Members multiply in their insect vectors.

Morphology

Virions enveloped and spherical about 70 nm in diameter and with glycoprotein spikes. There are four structural proteins (coat protein and three membrane glycoproteins).

Genome

Monopartite positive sense single-stranded RNA 11-12kb in length, with a 5'-cap and a 3'-polyA tail.

Genus Genomic Organization

There are two polyproteins, the second of which is translated from a subgenomic RNA. They are subsequently processed into a number of functional proteins:
  • Non-structural polyprotein (269-285 kDa):
    • Non-structural protein 1 (methyl transferase activity), 59-62 kDa
    • Non-structural protein 2 (helicase and protease activity), 88-95 kDa
    • Non-structural protein 3 (unknown function), 52-63 kDa
    • Non-structural protein 4 (polymerase activity), 68-70 kDa
  • Structural polyprotein (136-143 kDa):
    • Coat protein C, 29-32 kDa
    • Envelope protein E3, 6.5-7.9 kDa
    • Envelope protein E2, 46-48 kDa
    • 6K protein, 6-7 kDa
    • Envelope protein E1, 47-50 kDa

Type Member Genomic Organization

There are two polyproteins, the second of which is translated from a subgenomic RNA. They are subsequently processed into a number of functional proteins:
  • Non-structural polyprotein (280 kDa):
    • Non-structural protein 1 (methyl transferase activity), 60 kDa
    • Non-structural protein 2 (helicase and protease activity), 90 kDa
    • Non-structural protein 3 (unknown function), 60 kDa
    • Non-structural protein 4 (polymerase activity), 69 kDa
  • Structural polyprotein (137 kDa):
    • Coat protein C, 29 kDa
    • Envelope protein E3, 7.0 kDa
    • Envelope protein E2, 47 kDa
    • 6K protein, 6.2 kDa
    • Envelope protein E1, 47 kDa