Index >> Virus Structure and Classification >> Enveloped Constituents

Enveloped Constituents - Proteins

Viral envelopes contain host cell proteins as well as, proteins specified by the virus. In arboviruses, rhabdoviruses, and, myxoviruses, there is overwhelming evidence that all envelope proteins are coded by viral genomes.

In leukoviruses, herpesviruses and  poxviruses, it is not clear whether host cell proteins are present in the envelope or not. These viruses, however, do contain proteins specified exclusively by the virus.

The envelopes of rhabdoviruses, orthomyxoviruses and paramyxo viruses contain one major carbohydrate free polypeptide.

This protein is a glycoprotein. In the Sindbis virus and the Semliki Forest Virus the protein contains a relatively high propor­tion of hydrophobic amino acids, indicating that it is associated with the envelope lipids. Rhabdoviruses have one glycoprotein in. their envelopes, paramyxoviruses two glycoproteins and influenza viruses (orthomyxoviruses) four different glycoproteins.

The herpesviruses and the leukoviruses also have glycoproteins in their envelopes. The, spikes on the outer surface of virions are glycoproteins.

Carbohydrates

Viral envelopes contain a significant amount of carbohydrates. Galactose, man nose, glucose, fucose, glucosamine and galactosamine have been found in the influenza virus, the parainfluenza virus SV5 and in the Sindbis virus.