MIDTERM 2 Flashcards
What other viruses does the Single stranded RNA bacteriophage relate to?
Poliovirus and herpesvirus, We will focus on MS2
How many proteins do they code for
One for the structure and three other proteins
How is transcription regulated
because the virus is so small, the virus transcription is carefully regulated by the secondary structure of the RNA
What does the layout for the MST bacteriophage gene look like?
from 5’ to 3’, it is first the code for the maturation protein, then the coat protein, and then the replicase. The lyse protein is split between the replicase and the coat protein
Describe the structure of MSII
It is a naked capsid virus containing one maturation protein and a single stranded RNA genome inside. The RNA can immediately function as mRNA
What does the maturation protein do?
It helps prevent the RNA from degrading as well as helping to bind the bateriophage to the host
Who does the MSII target?
the male E.Coli due to their protruding tail called the f. pili
How does MSII enter the male e.coli
The maturation protein will bind to the f.pili of the e.coli, where it is then cleaved into two releasing the virion RNA where it will then enter the host
what is the general abundance of the proteins made by MSII
it makes 180 coat proteins in order to make the nucleocapsid
It makes one maturation protein
and only a few replicase
Why does MSII have to regulate transcription and replication separately?
Because the RNA strand on the MSII can serve as mRNA as well, transcription and replication happen on the same strand, but the ribosome and the replicase moves in opposite directions of each other. If they were to attach to the RNA at the same time, they would block each others path without being able to release
In basic terms how does regulation of the transcription vs. Replication occur
Replication by blocking the AUG binding sight for the ribosome attachment through the use of the secondary structure of the coat protein
What depends on the gene of the coat protein
The translation of the lysis protein
Ribosome attachment and replication
Shine-Dalgarno sequence
the ribosomal attachment binding site on the MSII
How is the replicase of MSII translated
As the coat protein is being translated, the large size of the ribosome will cause the secondary hairpin structure of the replicase to unfold exposing the originally blocked start codon site. This will initiate other ribosomes to bind to the start codon site allowing for the creation of replicase. After enough replicase has been created, a dimer will attache to the hairpin structure, preventing the ribosome for the coat protein to undo the structure and therefore prevent the translation of the replicase
How is the lysis gene translated in MSII
This is initiated at the end of the coat protein through the process of re-initiation. Once the ribosome reaches the stop codon, it will back track to the first AUG sight going back allowing for the creation of the lysis protein. This happens about 5% of the time and the ribosome can re-initiate either forward or backwards. This prevents the creation of ea
