Lecture 8 Flashcards
Properties of archea
- Unicellular microorganisms
- Circular chromosomes
- No nucleus and no nuclear enveloppe
- Cell walls made of impermeable S layer of proteins
- Special phospholipids on mmebrane
- Complex translation initiation mimicking eukaryotes
- Methionine, not N-formyl methionine, to start translation
- Histone-like proteins
- Complex RNA polymerase machinery
- DNA replication machinery alike eukaryotic counterparts
- Distinct ribosomal RNA sequences
- Live in extreme environments (volcanic hot springs,
salt lakes, etc.)
Viruses of archea
-different than phages and eukaryotic viruses
* Unusual morphology (lemon, droplet, bottle shapes, etc)
* All have dsDNA as genome (one has ssDNA)
* Most have internal or external lipid envelopes
* Many are temperate viruses that integrate their genome into host cell DNA
* Many do not have an identifiable DNA polymerase gene: they use the hosts polymerase
When were bacteriophages discovered and by who?
-Frederick Twort
Glassy transformation
1915
-Felix d’Herelle
Bacteriophage
1917
When did we see bacteriophages
1940 EM
Who got the nobel prize of physiology in 1978 and why
Werner Arber, Daniell Nathans and Hamilton for the discovery of restriction enzymes and their application to problems of molecular genetics
when was the first ms2 rna genome sequenced
1976
when was the first lambda dsrna genome sequences
1982
true or false: phage and bacteria don’t co evolve
false they do through gene transfer
true ro false; crispr is thanks to the co-evolution of phage and bacteria
true
what does the word phage come from
phagein which means to devour
true or false: phages don’t use the hosts biosynthetic machinery
false: they do most of the time either all or some
Names of the different phage morphology
caudovirales: tailed phages
-myoviridae aka contractile tail: T4 phages
-siphoviridae: non contractile flexible tail ex: lambda phage
-podoviridae: non-contractile short tail: t7
microviridae: spherical phage ex: φX174
Inoviridae: fibrous phage exL M13
MS2
- Single-stranded RNA bacteriophages
- Belong to levivirus genus
- Naked icosahedral capsid
- Linear single-stranded positive sense RNA, 4kb
-1 copy of the maturation protein
-180 copies of coat protein
-26nm long
why is the secondary structure of the phage rna important
because it regulates how the proteins are synthesized
replication of Ms2: go see your notes
explain the process
how are some of the stem loops opened
they are opened when a certain part of the genome has been translated by the ribosome
RNA folding kinetics regulate translation of
maturation protein
there is a short window when the rna is in this weird unstable conformation
-it’ll be open just long enough for the fmet maturation protein to be translated
MS2 genome replication
- Replicase binds to the start of coat gene to shut down
coat protein translation. - Replicase is associated with three host proteins,
S1 protein of the small ribosomal subunit,
translational elongation factors EF-Tu and EF-Ts. - S1 directs replicase to the start of coat gene.
- EF-Tu/GTP may help replicase to initiate RNA synthesis.
- EF-Ts recycles EF-Tu/GDP to EF-Tu/GTP
MS2 assembly
as more and more proteins are synthesized, these dimerize and that complex will be able to recognize and bind to the replicase operator hairpin -> shuts down the synthesis of replicase-> start formation of the capsid structure
-strong affinity for the operator and the proteins
each capsid has one copy of the rna
Application of MS2/RNA binding in monitoring
RNA under microscope
can look at the location and thanks to the mrna in other cells
-aka you can see when rna is transported
jX174
- Belong to Microviridae
- Microvirus
- Naked icosahedral capsid
- Circular single-stranded DNA
entry of jX174
*Capsid interacts with sugar residues (likely glucose)
in the lipopolysaccharide.
*DNA is delivered through the spikes
(containing G and H proteins).
*H protein mediates the penetration step thanks to its N-terminal transmembrane helix
viral genome replication of jX174 go see notes
explain
