July 2 classnotes: Virus Lytic Life cycle

**** Test !**** until 1:15 pm
 

Bio 280 Test 2 study notes:

Lecture notes: 7/2/2012

Lytic life cycle:  Fig. 13.8

Step 1: Attachment / Adhesion

 

Receptor proteins on host cell surface (specificity)

virus binds by ligand proteins:

Phage:tail fibers

Naked:capsomeres

Enveloped:peplomers

*drug target: attachment antagonists

********* group activity*********

* Label diagram:

A. peplomer

B. envelope (made from a cell membrane)

C. capsid

d. Capsomeres

e. genomen

* cde = nucleocapsid

* which of the lettered parts would b the ligand for the host cell surface proteins? A = peplomer

* not transmitted to water because enveloped so vulnerable outside body

****** print out sheet for after exam*****

Lytic Cycle: Stage 2

PENETRATION:

Phages: lysozymes: tail fibers (uncoating not needed)

Naked virus:

1. Endocytosis or phagocytosis: *uncoating in cytoplasm

2. Direct entry: capsomeres make a hole and inserts genome (does not need uncoating)

- attachment, insert, only genome enters

Fig 13.12

*** end result: genome floating in cytoplasm***

Enveloped: 1. Fusion of envelope and cell membrane fig 13.12

*must be uncoated in cytoplasm, can’t happen with naked virus because they don’t have envelope which used to be part of old host cell membrane

Ex. Herpoviruses, paramyxoviruses, HIV

2. Endocytosis

**** uncoating in cytoplasm****

***some drugs as uncoating inhibitors***

3, direct entry

Picture: entry>> uncoating>> (viral uncoating/ effective against influenza A virus) Amantadine and Flimantadine are two uncoating inhibitors>>> nucleic acid synthesis (virus enzyme directed) >>> viral particles production>>> exit

Lytic cycle: Step 3 Synthesis

Host genome shut down

·         may break up (phages, some animal viruses)

Genome of virus directs all cell activities:

·         produces viral parts:

o    genome copies

o    proteins

§  capsomeres

§  optional enzymes

§  peoplomeres and matrix , enveloped

Nucleic acid synthesis inhibitors: acyclovir, valcyclovir (vatrox), AZT… work against VIRAL synthesis of material but not our own….

Fig. 7.1

Fig 7.7

Master strand…. With start codon AUG….positive RNA makes sense to ribosome… + sense strand… starts with 3’ which is the master strand…. 5’ Holder strand….

Starts with UAC = negative sense RNA.. some viruses have negative sense RNA.. enzymes..

Posted blackboard outlines: