Togaviruses: Symptoms and Structure

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What is the size of the togavirus envelope particle?

70nm in diameter (correct)

50nm in diameter

120nm in diameter

100nm in diameter

How many copies of capsid proteins are present in the togavirus envelope?

360

180

240 (correct)

120

What type of RNA genome does the togavirus have?

'+' sense dsRNA

'-' sense ssRNA

'+' sense ssRNA (correct)

'-' sense dsRNA

Which cellular receptor does the E glycoprotein of togavirus bind to for receptor-mediated endocytosis?

Laminin receptor Signup and view all the answers

What is the role of nsP4 in the cytoplasm?

nsP4 acts as an RNA polymerase Signup and view all the answers

Where are structural proteins palmitoylated?

Golgi Signup and view all the answers

What is the function of E1 in the virus?

Component of virion envelope projections Signup and view all the answers

What happens when the pH drops in the endosome?

Conformational changes in E1/E2 heterodimer occur leading to fusion Signup and view all the answers

What is the role of 6K in the virus?

Involved in viral budding Signup and view all the answers

What is the function of PE2?

Precursor to E2, palmitoylated and glycosylated Signup and view all the answers

What is the fate of the viral genome once inside the cytoplasm?

It is released to be translated Signup and view all the answers

How do capsid proteins interact with envelope proteins during virus exit from the cell?

Capsid proteins bind to envelope proteins Signup and view all the answers

What are the symptoms of togavirus infection in animals and humans?

Symptoms range from rashes, high fever to joint pain and encephalitis. Signup and view all the answers

What is the significance of the term 'Latin Toga' in relation to the togavirus?

It refers to the virus envelope. Signup and view all the answers

Describe the composition of the togavirus envelope and capsid.

Envelope consists of 240 heterodimers of glycoproteins E1 and E2, capsid consists of 240 copies of capsid proteins. Signup and view all the answers

Explain the process of receptor-mediated endocytosis involving the E glycoprotein of togavirus.

E glycoprotein binds to cellular receptors, such as laminin receptor, via clathrin-coated vesicles. Signup and view all the answers

What are the conformational changes in the E1/E2 heterodimer triggered by in the endosome?

The pH drop in the endosome leads to conformational changes in the E1/E2 heterodimer, eventually leading to fusion after exposure of the fusion domain. Signup and view all the answers

What happens to the RNA genome once it is inside the cytoplasm?

Once inside the cytoplasm, the RNA genome is released to be translated. It may interact with cellular proteins to release the genome. Signup and view all the answers

What are the functions of nsP1, nsP2, and nsP4 in the cytoplasm?

nsP1 functions as an RNA capping enzyme, nsP2 functions as a cysteine proteinase and RNA helicase, and nsP4 functions as an RNA polymerase. Signup and view all the answers

What would happen if the RNA polymerase stopped at a specific codon?

If the RNA polymerase stopped at the codon, it would make protein 123. If it continued, it would make protein 123+4, as P4 is an RNA-dependent RNA polymerase. Signup and view all the answers

How are the structural proteins of the virus directed to different cellular locations?

The structural proteins are cleaved during translation and directed to different cellular locations. Signup and view all the answers

What is the fate of the polyprotein generated in the virus?

A polyprotein is generated and post-translationally cleaved by host signal peptidase and furin protease. Signup and view all the answers

What is the role of PE2 in the virus?

PE2 is a precursor to E2, palmitoylated and glycosylated. It contains the amino-terminal part of PE2 with the signal sequence, while E2 is the carboxy-terminal part of PE2, a component of virus envelope projections. Signup and view all the answers

How does the virus exit the cell?

The virus exits the cell by budding, where capsid proteins interact with the cytoplasmic tails of envelope proteins studding the plasma membrane. Signup and view all the answers