What are the 2 antibiotics that affect transcription?
Rifamycin B
Actinomycin D
What does Rifamycin bind to? Selectively binds to bacterial RNA polymerase and inhibits initiation
What does Actinomycin D bind to?
Nonselectivly binds to DNA and inhibits elongation.
Rifomycin B is used to treat tuberculosis and leprosy.
Actinomycin D is an anti-cancer drug which mimics and DNA base and blocks transcription elongation. Can inhibit DNA synthesis in normal cells.
List all types of RNAs: mRNA: encodes proteins rRNA: forms scaffolding on which ribosomes are built tRNA: Shuttles aa to ribosomes tmRNA: frees ribosome stuck on damaged mRNA catalytic RNA: carries out enzymatic reactions
which RNA is the easiest to degrade by RNases and why are the other 2 more stable? mRNA has a short life and is easily degraded. tRNA and rRNA are more stable due to their folded structures and presence of unusual modified nucleotides.
What is the central dogma?
DNA –DNA replication DNA-transcription mRNA—translation-> proteins
How many possible codons are out there?
64; 61 specify amino acids, 3 are stop codons
What is wobble?
When tRNA can recognize more than one codon at a time and it only base pairs with the first 2 positions of the codon and has an irregular base pairing at the 3rd position. This mismatch is called wobble.
What makes tRNAs so stable?
The unusual modified nucleotides.
What are the 2 regions of tRNA?
1)anticodon loop: where anticodon hydrogen bonds with codon on mRNA
2) 3’ CCA (acceptor end) : where amino acid binds
What enxymes carry out the charging of tRNA?
Aminoacyl tRNA synthetases.
What is ribosomes structure?
2 subunits: each subunit contains rRNA and proteins.
Prokaryotes: 50S subunit +30S = 70 S ribosome
30S = 16S rRNA molecule and 21 proteins
50S = 5S, 23 S and 31 proteins * How do you build a ribosome?
Its initially transcribed from a single RNA molecule
Specific RNAses cleave the transcript at precise places to release 16S, 23S and 5S rRNA and tRNA molecules.
Ecoli have 7 of these operons. All make the same rRNA abut different tRNAs. What are the 3 binding sites for tRNA on the 70S ribosomes?
1) A (acceptor) site: binds incoming aminoacyl tRNA
2) P (peptidyl-tRNA) site: harbors the tRNA with the growing polypeptide chain.
3) E (exit) site: binds a tRNA recently stripped of its polypeptide.
What’s peptidyltranferase: enzyme responsible for peptide bond formation is a ribozyme that’s part of 23S rRNA.
What is the Shine-Dalgarno sequence?
4-8 bps before the start codon.
5’ AGGAGGU 3’ its complimentary to a sequence found at the 3’ end of 16S rRNA What are the 3 steps of translation of RNA to proteins?
1) Initiation:brigs the 2 ribosomal subunits together. & places 1st aa
2) Elongation: adds aa as directed by mRNA.
3) Termination: releases the completed protein and recycles ribosomal subunits !
EACH PHASE REQUIRES A NUMBER OF PROTEIN FACTORS AND GTP ENERGY FORM. * * What are the proteins that initiation requires?
Initiation factors: 1) IF1,IF2 and IF3
What is the function of IF3?
It brings the mRNA and 30S ribosome unit together Which part of the ribosome finds the Shine-Dalgarno?
