Lecture 7 Flashcards
What are the three domains of life?
Bacteria, Archaea, Eucarya
What are archaea?
Unicellular microorganisms that have circular chromosomes and no nucleus
Archaea cell walls are made of ___
Impermeable S layer of proteins
True or false: Methionine, not N-formyl methionine, starts translation in archaea
True
What parts of archaea resemble eukaryotes?
Complex translation initiation
DNA replication machinery
Where can archaea be found?
Live in extreme environments
Describe archaea viruses
- Unusual morphology (lemon, droplet, bottle shapes)
- 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
When was the first MS2 RNA genome sequenced?
1976
When was the first phi-X174 ssDNA genome sequenced?
1977
When was the first lambda dsDNA genome sequenced?
1982
How do bacteria transfer genes?
Transformation: uptake of DNA
Transduction: bacteriophage packages host DNA and enters another bacteria (can be random DNA packaging or specialized)
PICIs: Packaging of genomic islands
GTA: Random packaging of GTA
Lysogenic conversion (not really gene transfer): Phage-encoded toxin enters into host DNA, bacteria produces toxin and it is either secrete or lyses the bacteria
What are the types of phage therapy?
Phage therapy: Bacteriophage infects pathogenic bacteria and then eliminates it
Phage enzyme: Phage produces enzyme that kills pathogenic bacteria
Biofilm dispersal: Phage produces biofilm that kills pathogenic bacteria
Drug sensitization: Phage injects drug-sensitive enzyme and cell dies when drug binds to enzyme
What is the word bacteriophage come from?
Bacteria and Greek word phagein (to devour)
What are bacteriophages?
Obligate intracellular parasites that multiply inside bacteria
Describe the MS2 bacteriophage
Single-stranded RNA bacteriophages
Belong to levivirus genus
Naked icosahedral capsid
Linear single-stranded positive sense RNA, 4kb
What does the MS2 attach to?
Sex pious of bacteria
M2 bacteriophage: which protein is produced first?
Coat protein
M2 bacteriophage: What does the translation of coat genes allow production of?
Replicate and lysis proteins
M2 bacteriophage: What do the replicate proteins do?
With the help of host proteins, binds to start codon of coat gene, blocks coat protein synthesis, copies + RNA into -RNA into +RNA
M2 bacteriophage: What happens when more coat proteins are produced?
They form dimers that shut down replicate production and initiate assembly of phage particles
Describe genome replication of MS2.
Replicate binds to the start of coat gene to shut down coat protein translation
Replicate is associated with three host proteins: S1 protein of the small ribosomal subunit, translational factors EF-Tu and EF-Ts
S1 directs replicate 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: Coat proteins nucleate at the _____
Replicase operator hairpin
Describe phiX174
Bacteriophage
Belong to Microviridae
Micro virus
Naked icosahedral capsid
Circular single-stranded DNA
What are the different components of phiX174?
DNA replication
Internal scaffolding protein
DNA packaging
External scaffolding proteins
Host cell lysis
Major capsid protein
Major spike protein
DNA pilot protein, DNA delivery
DNA binding, DNA packaging
Nonessential genes
How does phiX174 enter the cell?
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.
Describe the viral genome replication of phiX174
Review lecture lecture 7 slide 34
How many promoters and terminators does phiX174 have?
Three promoters
Four terminators
PhiX174: what controls the promoters and terminators?
Transcription strength of promoters
Stability of viral RNA
Termination efficiency of terminators
Ribosome binding site
How is the phiX174 capsid assembled?
Start with partially assembled protein (not monomer)
Internal scaffolding prote B helps create a spike protein G pentamer
External scaffolding protein D tetramer helps create procapsid
DNA packaging complex
Protein B discarded and becomes provision
Protein D discarded and becomes virion
