Steps 5-7: Assembly and Exit (Lecture 15) Flashcards
What are the 3 common de novo reactions necessary for viral reproduction?
forming structural unit, assemble capsid, incorporate genome
What are the 3 things that viral proteins need to interact with?
with each other, genome, lipid membrane (envelope viruses)
What are 4 host cell processes that viruses rely on and why?
chaperones (protein folding), transport systems, secretory pathways, and nuclear import/export
What is short distance viral movement dependent on?
protein channels
Where are protein channels found on?
plasma membrane, nuclear membrane, golgi
What is long distance movement dependent on?
cytoskeleton tracks such as motor proteins and microtubules
What kind of cytopathic effects do viruses cause that lead to inclusion bodies? What are inclusion bodies?
conentration of proteins on internal membranes due to viral factories; inclusion bodies are fragmented organelles
What are inclusion bodies called in rabies viruses?
Negri bodies
What does it mean when it says that viral proteins have zip codes?
viral proteins contain signal sequences
What role do the signal sequences have on the viral proteins?
helps them get to the targeted area where they need to go
What are the 4 types of zip codes?
membrane targeting, membrane retention, nuclear localization and retention signals
What are membrane targeting signals?
also can be fatty acid modifications that target these proteins to the membrane
What are membrane retention signals?
signals that retain the proteins on the membrane so that they don’t get secreted or go anywhere else
What are nuclear localization and export signals?
directs proteins that need to get in or out of the nucleus
What type of pathway does localization of viral proteins to plasma membrane?
secretory pathway
What are 3 ways that viruses assemble their protein coats?
assembly from individual protein molecules that will come together, from a polyprotein precursor that will fold on its own or get cleaved, or use chaperones
How does the virus distinguish which genome to package from the cellular DNA/RNA molecules during encapsidation?
based on packaging signals embedded on viral genome
What types of packaging signals do DNA viruses have?
located near inverted repeats and origin, it is complex
What types of packaging signals do RNA viruses have?
are often secondary structures and is varied
What is the mechanism of release for envelope virions?
assemble at and bud from plasma membrane OR via exocytosis
What is the mechanisms of release for non-enveloped virions?
induce cellular death pathway = causes membrane to rupture/bleb so virus can get out || lyse cell by puncturing holes on cell membrane via viral proteins || inhibit cellular pathways that can compromise structural integrity so the cell will fall apart and virus can get out
What are the 4 ways that viruses can obtain an envelope?
viral glycoproteins integrated into membrane interact with nucleocapsid proteins || use internal matrix proteins or capsid proteins to drive budding || membrane proteins themselves can drive budding || matrix proteins mainly drive budding but need additional components to increase budding efficiency
Where are membrane proteins synthesized?
rough endoplasmic reticulum
