A microbiologist analyzed chemicals obtained from an enveloped RNA virus—similar to a mumps virus—that infects monkeys. He found
that the viral envelope contained a protein characteristic of monkey cells. Which of the following is the most likely explanation? - The virus gets an envelope when it leaves the host cell.
- The virus forced the monkey cell to make proteins for its envelope.
- The virus is a prophage.
- Its presence is a result of the monkey's immunological response.
- The virus fools its host by mimicking its proteins.
The virus forced the monkey cell to make proteins for its envelope.
Explanation:Enveloped viruses contain nucleocapsids of either icosahedral (e.g. herpesviruses, togavirus) or helical symmetry (e.g. influenza). The outer envelope is a lipid bilayer derived from host cell membrane in which both viral glycoproteins and some host proteins are embedded.
Many enveloped viruses complete their replication cycle by forming vesicles that bud from the plasma membrane. Some viruses encode “late” (L) domain motifs that are able to hijack host proteins involved in the vacuolar protein sorting (VPS) pathway, a cellular budding process that gives rise to multi vesicular bodies and that is topologically equivalent to virus budding. Although many enveloped viruses share this mechanism, examples of viruses that require additional viral factors and viruses that appear to be independent of the VPS pathway have been identified. Alternative mechanisms for virus budding could involve other topologically similar process such as cell abscission, which occurs following cytokinesis, or virus budding could proceed spontaneously as a result of lipid microdomain accumulation of viral proteins. Further examination of novel virus-host protein interactions and characterization of other enveloped viruses for which budding requirements are currently unknown will lead to a better understanding of the cellular processes involved in virus assembly and budding.
