Chapter 3 Flashcards
Nucleocapsid
Minimum Components
Nucleic Acid
Protein coat (“capsid”)
Other Components in some viruses
Envelope Spikes Own enzymes Matrix proteins Ions
(+) RNA
plus-sense
same sequence ad mRNA, may function as mRNA
(-) RNA
minus-sense
complementary to mRNA, cannot direct protein synthesis
Direct Terminal Repeat
true repeat (same sequence)
Inverted Terminal Repeat
repeat of complementary sequence; repeat the opposite orientation at the end
ssRNA with ITR can cirularize
Why vial genomes so small? (genetically compact)
nogenes for generating energy of enzymes for protein synthesis
Very few non-coding regions
Overlapping Genes
Multifunctional Genes
Structural Proteins
Virion components: capsid proteins and other proteins in virion
Structural proteins major functions
protect genome
Recognize and attach to host cell
Facilitate viral entry into host cell
Non-structural proteins
not virion components
non-structural proteins functions
enzymes
Transcription factors
Primers
Interference with immune response
Viral Structure Advantages
minimize coding requirements
Energy efficient in viral assembly
Capsids are strong, stable, can self-assemble
Capsid Strutures
Icosahedral Helical Conical or rod-shaped bullet tailed
Icosahedral Structure
Regular Polyhedron 20 faces each triangle made of 3 protein molecules 12 vertices(corners) 1 pentamer (5 protein molecule) at each vortex 30 edges Minimum 60 subunits Very common in many viruses
Helical Structure
Hollow helical protein tube identical protein molecules Rigid(in many plant viruses) Flexible (in many animal viruses) All proteins interact equivalently with each other with nucleic acid In many ssRNA viruses
