Lecture 14 - The ribosome Flashcards
What is the rate of translation?
10-20aa per second
What are the A, P, and E sites on the peptidyl transferase centre?
The A site is where the incoming amino acylated tRNA can attach.
The P site harbors the polypeptide chain
The E site is the exit site of the deacylated tRNA.
These sites are common to both subunits.
Explain the structure of the 30s subunit.
0.8 MDa in size
21 proteins on the surface
1500 nucleotides rRNA
Explain the function of the 30s subunit.
Initiates binding to the mRNA via initiation factors at the Shine-Dalgarno sequence.
Ensures correct translation takes place via the decoding center
Explain the structure of the 50s subunit.
1.5MDa in size
34 proteins on the surface
3000 nucleotides of rRNA
Explain the function of the 50s subunit.
Peptide bond formation occurs here
What domain in the 50s subunit houses the peptidyl transferase center?
Domain V (5)
What are the properties of ribosomal proteins?
It is made up of 55 proteins.
Most proteins have one or more globular domains
Globular domains located on the surface, extensions and loops buried within the structure.
They recognize RNA through shape and charge complementarity.
What are initiation, elongation and termination factors in translation?
Initiation factors: Assemble ribosome onto the mRNA
Elongation factors: Permit production of the polypeptide chain.
Termination factors: Halt protein synthesis
Name two elongation factors and their function.
Ef-Tu: Delivers aminoacyl tRNA to the ribosome
EF-G: Promotes translocation of tRNAs during synthesis
They bind to the bL12 stalk. (ribosomal stalk region)
Where is the ribosomal exit tunnel located and what are its dimensions?
It is located within the 50s subunit
100A in length, 20A width.
The tunnel wall is lined with 23s rRNA and is constricted by loops.
It also permits limited folding.
