Ribosomes and mechanism of translation Flashcards
What subunits is a prokaryotic ribosome made up of?
70S: 50S + 30S
What subunits is a eukaryotic ribosome made up of?
80S: 60S + 40S
What is the weight of a prokaryotic ribosome?
2.3 x 10^6 daltons
What is the weight of a eukaryotic ribosome?
4.6 x 10^6 daltons
What percentage of the prokaryotic ribosome is RNA by mass?
65%
What percentage of the eukaryotic ribosome is RNA by mass?
60%
What subunits is a prokaryotic 50S subunit made up of?
23S RNA + 5S RNA
How many ‘L’ proteins does the prokaryotic 50S subunit have?
31
What subunit is a prokaryotic 30S subunit made up of?
16S RNA
How many ‘S’ proteins does the prokaryotic 30S subunit have?
21
What subunits is a eukaryotic 60S subunit made up of?
25S-28S RNA and 5.8S +5S RNA
What subunits is a eukaryotic 40S subunit made up of?
17S-18S RNA
How many ‘L’ proteins does the eukaryotic 60S subunit have?
45-50
How many ‘S’ proteins does the eukaryotic 40S subunit have?
~30
Are there many proteins at the subunit interface of ribosomes?
Very few
The 60S ribosome subunit has ‘extra’ what mainly on its back (non-interface) surface?
‘Extra’ proteins
Where do protein-protein interactions occur in eukaryotic ribosomal subunits?
On the ‘outside’ of the subunits
Where do protein-protein interactions occur in eukaryotic ribosomal subunits?
On the ‘outside’ of the subunits
Many ribosomal proteins have bizarre structures that are quite unlike what?
Globular proteins
Give an example of a protein that contains a bizarre structure in a ribosome
Protein L15
What do the ribosomal proteins that contain bizarre structures act like?
Hairpins: they form extended scaffolds on which rRNA is supported
What do the ribosomal proteins that contain bizarre structures act like?
Hairpins: they form extended scaffolds on which rRNA is supported
Are the decoding and peptidyl transferase centre (PTC) on the same ribosomal subunit?
No
What does tRNA bridge?
The ribosomal subunit interface (water-free zone)
EF-Tu and EF-G are examples of what biological phenomenon?
Molecular mimicry
What does RF1 recognise?
UAG and UAA
What does RF2 recognise?
UAA and UGA
What enzyme is associated with RF3?
GTPase
What are the stop codons?
UAG, UAA, UGA
What does the ribosome release factor (RRF) plus EF-G generate?
Free 70S subunit
During the initiation of translation in bacteria, what binds to the 30S subunit?
Proteins bind
Act as anti-association factors
What is the recognition called between the 30S subunit and mRNA during the initiation of translation in bacteria?
Shine-Dalgarno (S-D) recognition
How many tRNAmet does E. coli have?
2: Initiator tRNA (tRNAf) used at AUG or GUG - start codons Ordinary tRNA used at internal AUG
What initiates translation in bacteria?
Formyl-methionine
What enzyme catalyses the reaction of met-tRNAf into fmet-tRNAf?
Transformylase
