Viral Structure Flashcards
(109 cards)
1
Q
are elegant assemblies of viral, and
occasionally cellular, macromolecules. (50-90% protein).
A
virion (virus particles)
2
Q
virions are what percent protein
A
50-90 percent
3
Q
come in many sizes and shapes and vary
enormously in the number and nature of the molecules
from which they are built.
A
virus particles
4
Q
predicted that the only two ways in
which asymmetric subunits could be assembled to form
virus particles would generate structures with either cubic
or helical symmetry.
A
Watson and Crick
5
Q
Watson and Crick predicted that the only two ways in
which asymmetric subunits could be assembled to form
virus particles would generate structures with either __ or __ symmetry
A
cubic
helical
6
Q
virion function (2)
A
protection of the genome
delivery of the genome
7
Q
Assembly of a stable protective protein shell.
Specific recognition and packaging of the nucleic acid genome .
Interaction with host cell membranes to form the envelope
what function of virion
A
protection of genome
8
Q
Binding to external receptors of the host cell.
Transmission of signals that induce uncoating of the genome Induction of fusion with host cell membranes.
Interaction with internal components of the infected cell to direct transport of the genome to the appropriate site .
what function of virion
A
delivery of the genome
9
Q
other functions of virion
A
Interactions with cellular components for transport to intracellular sites of assembly.
Interactions with cellular components to ensure an efficient infectious cycle.
10
Q
single, folded polypeptide chain
A
subunit (protein subunit)
11
Q
A
11
Q
unit from which capsids or nucleocapsids are built; may comprise one protein or multiple, different protein subunits
A
structural unit
12
Q
the protein shell surrounding the nucleic acid genome
A
capsid
13
Q
nucleic acid protein assembly packaged within the virion; used when this is a discrete substructure of a particle
A
nucleocapsid
14
Q
the host cell derived lipid bilayer carrying viral glycoproteins
A
envelope (viral membrane)
15
Q
infectious virus particle
A
virion
16
Q
main viral structrures and general morphology (6)
A
core nucleic acid types
capsid
envelope
envelope glycoprotein enzymes
non-genomic viral nucleic acid
cellular macromolecules
17
Q
core nucleic acid type (4)
A
dsDNA
ssDNA
dsRNA
ssRNA
18
Q
Code for viral proteins:
special enzyme,
inhibitory proteins,
structural proteins
A
core nucleic acid
19
Q
subunit of a capsid
A
capsomeres
20
Q
capsids are multiple copies of one ___
A
protein
21
Q
a capsid and a nucleic acid makes up a
A
nucleocapsid
22
Q
capsid is shaped
A
helical or icosahedral
23
Q
envelope is made up of
A
lipids, proteins, and carbohydrates
24
Derived from
membrane of host cell
envelope
25
part of viral envelope that help virus attach
to cells prior during
infection
spikes
26
do all viruses have envelope?
no
27
the protein coat that encases and protects the
nucleic acid genome
capsid or nucleocapsid
28
most virus particles appear to be ___ shaped or ___under the
electron microscope.
rod, spherical
29
construction of capsids from a small number of subunits would
minimize the genetic cost of encoding structural proteins -Such is ____
genetic economy
30
viruses use a smart strategy to build their protective shells efficiently, using minimal genetic instructions
genetic economy
31
repetition of such inter-actions among a limited number of proteins
results in a regular structure, with symmetry that is determined by the
spatial patterns of the interactions. In fact, the protein coats of many
viruses do display what symmetry
helical or icosahedral
32
- protein coat surrounding and
protecting the viral genome
viral capsid
33
collection or assembly of protein
molecules making up a viral capsid
capsomere
34
structure that consists of lipid
containing layers
viral envelope
35
type of symmetry of capsomere
arrangement associated with spiral-shaped viruses
helical
36
roughly spherical geometric structure
with 20 triangular faces and the most efficient
arrangement of capsomeres in a viral capsid.
icosahedral
37
viruses can have a range of shape and symmetries (4)
helical capsid
icosahedral capsid
multiple helical capsid in a spherical viral envelope
complex capsid (icosahedral head, helical tail)
38
structure of baceriophage
icosahedral head
helical tail
39
nucleocapsids of some enveloped animal viruses, as well as plant viruses and bacteriophages are shaped ___ or ___ Structures with helical symmetry
rod-like
filamentous
40
described by the number of structural units per turn of the helix
nucleocapsid
41
any volume can be enclosed by varying the length of the helix vs icosahedral symmetry with a fixed ____ volume
internal
42
virus that comprises of one single molecule of strand RNA, about 6.4kb in length, enclosed within a helical protein coat
tobacco mosaic virus
43
repetitive intreactions among coat protein subunits form ___ in turn assemble as a long, rod-like, right handed helix
disks
44
repetitive intreactions among coat protein subunits form disks in turn assemble as a long, rod-like, ___handed helix
right
45
each coat protein binds ___ nucleotides of the RNA genome
three
46
made up of 20 triangular faces, five at the top, five at the
bottom and10 around the middle, with 12 vertices .
icosahedral symmetry
47
how many axes in icosahedral symmetry
three axes by two-,three-,five fold axes
48
Each of 20 faces of an icosahedron is an ___
triangle, and five such triangles interact at each of the 12
vertices
equilateral
49
a ____of a single viral protein (the subunit)
corresponds to each triangular face of the icosahedron
trimer
50
As an icosahedron has ___faces, ____identical subunits (3
per face 20 faces) is the minimal number needed to
build a capsid with icosahedral symmetry.
20
60
51
accommodation of viral genomes
necessitates a high degree of
condensation and compaction.
packaging the nucleic acid genome
52
binding of viral nucleic acids to capsid
proteins appears to provide sufficient
___ ___required to achieve
packaging
energy force
53
how many mechanisms for condensing and
organizing nucleic acid molecules within
capsids can be distinguished
three
54
three packaging of nucleic acid genome
direct contact with a protein shell
packaging by specialized viral protein
packaging by cellular proteins
55
nucleic acid makes direct contact with the protein(s) that
forms the protective shell of the virus particle
*advantageous arrangement for viruses with small
genomes
what packaging
direct contact of the genome with a protein shell
56
*nucleocapsid proteins ; important function of such
proteins is to condense and protect viral genomes
what type of packaging
packaging by specialized viral protein
57
circular, double-stranded DNA genomes of these
viruses are organized into nucle-osomes that contain
the four core histones, H2A, H2B, H3, and H4 -like a
minichromosome
what kind of packaging
packaging by cellular proteins
58
envelope formed by a viral protein-containing
membrane that is derived from the host cell,
but they vary considerably in size,
morphology, and complexity.
viral envelope
59
viral envelope vary in
lipid composition
number of protein
location
60
phospholipids in viral envelope have different names such as
phosphatidylcholine
phosphatidylethanolamine
phosphatidylserine
61
form the outermost layer of enveloped animal
viruses, but in bacteriophages and archaeal
viruses of the PRD1 family the membrane lies
beneath an icosahedral capsid
viral envelope
62
viral envelope form the outermost layer of enveloped animal
viruses, but in bacteriophages and archaeal
viruses of the PRD1 family the membrane lies
beneath an ___ ____
icosahedral capsid
63
integral membrane proteins firmly embedded in the lipid bilayer by a short membrane-spanning domain
viral glycoproteins
64
binding sites for cell surface virus receptors, major antigenic determinants, and sequences that mediate fusion of viral with cellular membranes during entry
external domains
65
separate large external domains with oligosaccharides from smaller internal segments
hydrophobic a-helix
66
hydrophobic a-helix separate large external domains with ___ from smaller internal segments
oligosaccharides
67
make contact with other components of the virion, are often essential for virus assembly
internal domains
68
Viral envelopes mainly consist of
envelope proteins (E)
membrane proteins (M)
spike proteins (S)
69
involved in viral host binding and
subsequent virus-host membrane
fusion to establish the pathogenesis
of the virus.
viral fusion proteins
70
SARS Coronavirus possess a ___
glycoprotein, which itself performs
the membrane fusion for the entry of
the virion and its fusion with host cell
spike glycoprotein
71
three modes of interaction between the internal domains of viral glycoproteins and viral capisd or nucleocapsids
direct protein-protein interactions
scaffolding proteins
lipid rafts and membrane microdomains
72
Viral glycoproteins can directly interact with capsid or nucleocapsid proteins through specific binding sites.
what modes of interaction between the internal domains of viral glycoprotein and viral capsids
direct protein-protein interaction
73
what modes of interaction between the internal domains of viral glycoprotein and viral capsids
Some viruses use ___proteins to mediate interactions between glycoproteins and capsid or nucleocapsid proteins.
scaffolding proteins
74
what modes of interaction between the internal domains of viral glycoprotein and viral capsids
In enveloped viruses, glycoproteins are often localized in this interactions where specialized regions of the host cell membrane facilitate the interaction between glycoproteins and capsid or nucleocapsid proteins during viral assembly and budding. This mechanism is particularly important for viruses like HIV and influenza
lipid rafts and membrane microdomains
75
DNA will need to bring its own DNA polymerase when it needs to replicate in the ___
cytoplasm
76
virus particles contain ___ necessary for synthesis of viral nucleic acid
enzymes
77
catalyze reactions unique to virus-infected cells
enzymes
78
enzymes catalyze reactions unique to virus-infected cells such as
synthesis of viral mRNA from RNA template or of viral DNA from RNA template
79
necessary because transcription of viral double stranded DNA genome takes place in the cytoplasm of infected cells vs cellular DNA-dependent RNA polymerases and RNA processing restricted to the nucleus
enzyme
80
other type of enzyme found in virus particles include
integrase
cap-dependent endonuclease
proteases
81
is a crucial enzyme produced by retroviruses, such as HIV, that enables the integration of viral DNA into the host cell's chromosomal DNA
integrase
82
is an enzyme involved in the "cap-snatching" mechanism used by certain viruses, such as influenza, to initiate the transcription of their mRNA. This process allows the virus to hijack the host cell's machinery for its own replication.
cap-dependent endonuclease
83
also known as peptidases or proteinases, are enzymes that catalyze the breakdown of proteins by cleaving peptide bonds between amino acids.
proteases
84
enzyme in human adenovirus that produces infectious particles
L3 23K
85
protein in Herpes simpelx virus that function in capsid maturation for genome encapsidation
VP24
86
protein enzyme for protein kinase in herpes simplex virus type 1
UL3
87
protein enzyme that act as RNase
herpes simplex virus type 1
88
protein that is an RNA-dependent RNA polymerase; synthesis of viral mRNA and vRNA; cap-dependent endonuclease in influenza A virus
P proteins
89
protein enzyme in vaccinia virus that is used to synthesize viral mRNA
DNA dependent RNA polymerase
90
protein enzyme in vaccinia virus that is used to synthesize poly (A) on viral mRNA
poly (A) polymerase
91
protein enzyme in vaccinia virus that is used to add 5' caps to viral pre-mRNA
capping enzyme
92
protein enzyme in vaccinia virus that is used to sequence specific nicking of viral DNA
DNA topoisomerase
93
protein enzyme in vaccinia virus that is used in virus particle morphogenesis
proteases 1 and 2
94
more complex particles may contain additional viral proteins that are ___ but are important for an efficient infectious cycle
enzymes
95
viral proteins used for viral genome replication
protein primers
96
___ proteins of herpesviruses such as the VP16 protein is used to activate transcription of viral immediate-early genes to initiate the viral program of gene expression
tegument
97
which virus contain viral mRNAs
adenovirus
herpesvirus
retrovirus particles
98
A limited set of viral mRNAs, as well as some cellular
and artificial reporter mRNAs, are packaged into
particles of human ____, a
betaherpesvirus that is an important human pathogen
cytomegalovirus
99
viral mRNAs are translated soon after delivery to the
____ cell
host cell
100
difficult to exclude the possibility that their pres-ence
is a functionally irrelevant and secondary
consequence of nonspecific nucleic acid binding by
viral structural pro-teins.
non genomic viral nucleic acid
101
viral particles contain cellular macromolecules such as ___ that condense and organize polyomaviral and papillomaviral DNAs
histones
102
because of ___, envelope viruses can readily incorporate cellular proteins and other macromolecules
budding
103
as bud enlarges and pinches off during virus assembly, internal ___ components may be trapped within it
cellular
104
primer for initiation of synthesis of the neg strand DNA during reverse transcription in retroviral genomes is a specific ___
tRNA
105
is incorporated into virus particles by virtue of its binding to a specific sequence in the RNA genome and to reverse transcriptase
tRNA
106
unusual properties of HIV type 1 is the presence of ____, a chaperone that assist or catalyzes protein folding
cellular cyclophilin A
107
cellular membrane proteins such as ___ and ___ can also be incorporated in the viral enveloped and can contribute to attachment and entry of retroviral particles
Icam-1 and Lfa1
108
