BIOC20 LECTURE 3 EXAM QUESTIONS AND ANSWERS
WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
T/F: most viral envelope proteins are type II integral proteins.
False. Most are type I
what are type I integral membrane proteins?
They are a class of viral envelope proteins.
N-terminus faces outward and the transmembrane anchor nearest the c-terminus of the
polypeptide facing inside
what are type II integral membrane proteins?
They are a class of viral envelope proteins that have the opposite orientation as type I.
The C-terminus is facing outward and the anchor is near the N-terminus.
what kind of signal sequence do type I env proteins have?
they have a ss that is cleaved at the N-term when they are inserted in the ER during
synthesis
what kind of signal sequence do type II env proteins have?
the transmembrane anchor acts as the ss, but is not cleaved off
What is the function of scaffolding proteins?
They assist with the formation of the procapsid (a precursor particle made by co-
assembly with capsid proteins).
They are not included in the mature final virion
, Dismantling of the scaffold yields the mature virion
how does the herpesvirus package its dsDNA genome?
encapsidates viral genome into a preassembled capsid/procapsid. Portal protein is used
to help DNA entry. The translocation of the DNA into the procapsid is energy dependent
and uses an ATP-driven motor.
This creates a mature virion that is in an energetically meta-stable state --> has stored
energy that can cause a spring-like release of viral genome upon infection
what are packaging signals, and give examples.
packaging signals govern the specificity for incorporation of viral genomes into virions --
> unique to different viruses
ex: genome forms a stem-loop structure or has negative charges that interacts with
positive charges on capsid proteins
ex: linear RNA strands fitting inside the groove of a helical structure like a "zipper" -->
assembly advantage
what are core proteins?
they are proteins that can accompany viral DNA genomes to condense them for optimal
packaging.
The proteins can be viral or histones from the host (similar to chromatin packaging)
WITH COMPLETE SOLUTIONS VERIFIED LATEST UPDATE
T/F: most viral envelope proteins are type II integral proteins.
False. Most are type I
what are type I integral membrane proteins?
They are a class of viral envelope proteins.
N-terminus faces outward and the transmembrane anchor nearest the c-terminus of the
polypeptide facing inside
what are type II integral membrane proteins?
They are a class of viral envelope proteins that have the opposite orientation as type I.
The C-terminus is facing outward and the anchor is near the N-terminus.
what kind of signal sequence do type I env proteins have?
they have a ss that is cleaved at the N-term when they are inserted in the ER during
synthesis
what kind of signal sequence do type II env proteins have?
the transmembrane anchor acts as the ss, but is not cleaved off
What is the function of scaffolding proteins?
They assist with the formation of the procapsid (a precursor particle made by co-
assembly with capsid proteins).
They are not included in the mature final virion
, Dismantling of the scaffold yields the mature virion
how does the herpesvirus package its dsDNA genome?
encapsidates viral genome into a preassembled capsid/procapsid. Portal protein is used
to help DNA entry. The translocation of the DNA into the procapsid is energy dependent
and uses an ATP-driven motor.
This creates a mature virion that is in an energetically meta-stable state --> has stored
energy that can cause a spring-like release of viral genome upon infection
what are packaging signals, and give examples.
packaging signals govern the specificity for incorporation of viral genomes into virions --
> unique to different viruses
ex: genome forms a stem-loop structure or has negative charges that interacts with
positive charges on capsid proteins
ex: linear RNA strands fitting inside the groove of a helical structure like a "zipper" -->
assembly advantage
what are core proteins?
they are proteins that can accompany viral DNA genomes to condense them for optimal
packaging.
The proteins can be viral or histones from the host (similar to chromatin packaging)
