Notes on Genus: Phlebovirus

enveloped spheres

Type member: Rift Valley fever virus

Contents

Members of this Genus
General Description
Morphology
Electron Micrograph
Genome
Genus Genomic Organization
Genome Map
Type Member Genomic Organization
Curated Sequences

General Description

This is one of the four animal virus genera in the family Bunyaviridae and is characterised by its ambisense coding strategy of the N and NSs genes on the S segment. The name refers to the phlebotomine vectors of the sandfly fever group of viruses.

Morphology

Virions pleomorphic in shape and size, spheroidal and enveloped, 80-110 nm in diameter. 3 filamentous nucleocapsids per envelope, each 200-3000 nm long (depending on arrangement) and 2-2.5 nm in diameter. Symmetry helical.

Virions composed of 1-2 % nucleic acid, over 50 % protein and 20-30 % lipid.

Genome

Linear, tripartite negative sense ssRNA: L (c.6400 nt), M (3200-4200 nt) and S (c.1700-1900 nt).

Genus Genomic Organization

Translation of the RNAs produces a polymerase (RNA-L; complementary sense), a protein precursor which is cleaved into two glycoproteins (RNA-M; complementary sense), and two proteins from RNA-S, the coat protein in the complementary sense and a non-structural protein in the virion sense.

Type Member Genomic Organization

The translation strategy is:
  1. RNA-L produces a single protein (L) of 243.6 kDa (RNA polymerase) in the complementary sense
  2. RNA-M produces a protein precursor of 132.0 kDa in the complementary sense, from which two proteins are generated:
    • Glycoprotein G1 (56.5 kDa)
    • Glycoprotein G2 (58.8 kDa)
  3. RNA-S produces the N (nucleocapsid, or coat protein) protein of 27.4 kDa in the complementary sense and
  4. a non-structural protein NSs of 29.9 kda in the virion sense