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 reflects the composition of the membrane from which viral envelopes were derived?

Lipid content

What interacts directly with the cytoplasmic tails of envelope proteins (viral spikes) during budding?

Nucleocapsid

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

Glycoproteins (spikes) Signup and view all the answers

What are the main criteria used to group virus species into genera?

Genome organization and size Signup and view all the answers

Which type of virus tends to have a reverse transcriptase (RT) step in their replication cycle?

Viruses with RNA genomes Signup and view all the answers

What is a characteristic of most '' RNA genomes that are less than 10kb?

They are small and have few genes Signup and view all the answers

Which type of virus tends to have fragmented genomes and capsids with icosahedral symmetry?

Viruses with dsRNA genomes Signup and view all the answers

What is a characteristic of all '' strand viruses that infect vertebrates?

They are enveloped Signup and view all the answers

What do satellite viruses encode?

Their own capsid proteins Signup and view all the answers

What is a characteristic of viroids?

They replicate only in the presence of a helper virus Signup and view all the answers

What are the main criteria used to group virus genera into families?

Genome organization and size Signup and view all the answers

Which type of virus tends to have an envelope?

Viruses with dsDNA genomes Signup and view all the answers

What is a characteristic of viruses with ssDNA genomes?

They do not have an envelope Signup and view all the answers

What is a characteristic of most dsRNA viruses?

They have capsids with icosahedral symmetry Signup and view all the answers

What is a characteristic of satellite nucleic acids?

They are encapsidated by the helper virus capsid Signup and view all the answers

Which type of integral membrane proteins have different orientations and signal sequences for membrane insertion?

Type II 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 do?

Direct the specificity of genome incorporation into virions Signup and view all the answers

What do core proteins associated with the viral genome inside the capsid do?

Neutralize negative charges on DNA and condense the viral DNA 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

How can virions release their genomes?

Proteolytic cleavage of capsid proteins Signup and view all the answers

What triggers the energetic metastability of virions for dissociation?

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

What are the criteria for virus classification?

Molecular architecture, genetic relatedness, and host organism Signup and view all the answers

What does capsid assembly vary based on?

Size, shape, and genomic composition Signup and view all the answers

What is the function of the ectodomain of Hemagglutinin (HA) from influenza virus?

Cell receptor binding Signup and view all the answers

What prevents viral aggregation and dehydration?

Glycosylation of viral surfaces Signup and view all the answers

What may involve different mechanisms depending on the virus type?

Budding 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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