Viral Envelope Glycoproteins and Capsid Assembly Quiz

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Questions and Answers

What is the process of developing viral envelopes at the cell membrane called?

Budding

What is the composition of viral envelopes similar to?

Cellular membrane

What is wrapped in a membrane into which viral glycoproteins have been inserted?

Nucleocapsid

What do some nucleocapsids interact directly with during budding?

Cytoplasmic tails of envelope proteins (viral spike) Signup and view all the answers

What do some viruses use to interact with both viral spikes and nucleocapsids during budding?

Matrix (M) protein Signup and view all the answers

What does the lipid content of the lipid bilayer reflect?

The composition of the membrane it was derived from Signup and view all the answers

What is inserted into the lipid membrane to form the viral envelope?

Glycoproteins (spikes) Signup and view all the answers

What can be used, aside from lipid analyses, to determine where a virus budded from?

Electron analysis Signup and view all the answers

What is the nature of viral envelopes in terms of symmetry?

Not always symmetrical Signup and view all the answers

Where can the process of budding occur?

Cell surface membrane or internal membranes (e.g. endoplasmic reticulum) Signup and view all the answers

How are virus species grouped into genera?

By genome organization, size, and replication strategies Signup and view all the answers

What is a characteristic of most '-' RNA genomes with less than 10kb?

They do not have envelopes Signup and view all the answers

What is a unique mechanism of transcription for dsRNA viruses?

Capsids act as tiny intracellular machines Signup and view all the answers

What distinguishes satellite nucleic acids from satellite viruses?

Satellite nucleic acids encode no proteins Signup and view all the answers

How are plant viruses typically named?

After the host plant species and disease symptoms caused Signup and view all the answers

What characteristic distinguishes viruses with dsDNA genomes?

They include some of the largest known viruses Signup and view all the answers

What is the function of reverse transcriptase (RT) in certain viruses?

To make a DNA copy of RNA in their replication cycle Signup and view all the answers

What is a characteristic of satellite viruses?

They only encode their own capsid proteins Signup and view all the answers

What distinguishes viroids from other viruses?

They do not encode for proteins Signup and view all the answers

How are bacteriophages typically named?

Include name of the host bacterial genus and an arbitrary number Signup and view all the answers

What is the function of glycosylation of viral surfaces?

Prevents dehydration and reduces protein-protein interactions Signup and view all the answers

What do packaging signals on viral genomes interact with to direct the specificity of genome incorporation into virions?

Capsid proteins Signup and view all the answers

What drives the formation of viral envelopes by budding?

Interactions between viral proteins Signup and view all the answers

What can trigger the release of virion genomes?

Proteolytic cleavage of capsid proteins Signup and view all the answers

How are viruses classified based on molecular architecture and genetic relatedness?

Comparing genomic and amino acid sequences Signup and view all the answers

What is the role of hemagglutinin (HA) from influenza virus?

Cell receptor binding Signup and view all the answers

What do integral membrane proteins Type I and Type II have different of?

Orientations and signal sequences for membrane insertion Signup and view all the answers

What is the role of core proteins associated with the viral genome inside the capsid?

Neutralize negative charges on DNA and condense the viral DNA Signup and view all the answers

What drives budding of virions involving membrane curvature and localized protein aggregates?

Interactions between envelope glycoproteins, matrix proteins, or nucleocapsids Signup and view all the answers

What triggers the dissociation of virions?

Binding to a receptor or protein on the cell surface or in the cytoplasm Signup and view all the answers

Study Notes

Viral Envelope Glycoproteins and Capsid Assembly

Envelope glycoproteins have large glycosylated ectodomains, hydrophobic transmembrane anchor domains, and short internal tails, synthesized in the ER and inserted into the plasma membrane via standard export pathways.
There are two types of integral membrane proteins, Type I and Type II, each with different orientations and signal sequences for membrane insertion.
Hemagglutinin (HA) from influenza virus has an ectodomain for cell receptor binding, a transmembrane anchor domain, and a cytoplasmic tail.
Glycosylation of viral surfaces prevents dehydration and reduces protein-protein interactions to prevent viral aggregation.
Capsid assembly varies based on size, shape, and genomic composition and may involve scaffolding proteins and concatemer formation to fill the genome.
Packaging signals on viral genomes interact with capsid proteins to direct the specificity of genome incorporation into virions.
Core proteins associated with the viral genome inside the capsid neutralize negative charges on DNA and condense the viral DNA for optimal packaging, resembling chromatin.
Interactions between viral proteins drive the formation of viral envelopes by budding, involving membrane curvature and localized protein aggregates.
Budding can be driven by interactions between envelope glycoproteins, matrix proteins, or nucleocapsids, and may involve different mechanisms depending on the virus type.
Virions can release their genomes through proteolytic cleavage of capsid proteins, unspooling of the genome, or interaction with cytoplasmic components.
Virions are energetically metastable and can easily dissociate with the right trigger, such as binding to a receptor or protein on the cell surface or in the cytoplasm.
Virus classification is based on molecular architecture, genetic relatedness, and host organism, with criteria including nucleic acid genome type, strandedness, topology, capsid symmetry, and presence or absence of an envelope. Comparing genomic and amino acid sequences helps determine genetic relatedness.

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