tRNA Flashcards
What are common features of all tRNA?
All contain ~75 bases
All exhibit a cloverleaf motif w/four loops and stems
All contain several different types of modified bases
All contain the sequence CCA at the 3’ terminus
Name the 4 tRNA loops
Anticodon loop
D loop
TYC loop
Variable loop
What part of the tRNA interacts with the mRNA codons during protein synthesis?
Anticodon loop
What is the difference between tRNA processing in prokaryotes and eukaryotes?
Prokaryotic tRNA is often synthesized as multimeric precursors while eukaryotic tRNA precursors are monomeric. Eukaryotic tRNA also requires splicing of a short intron sequence
What two ribonuclease are involved in prokaryotic tRNA processing and what are their actions?
RNase P cleaves on the 5’ side
RNase D cleaves on the 3’ side
What processing steps occur in eukaryotic tRNA?
Removal of 5’ leader
Removal of 3’ bases and addition of CCA
Removal of short intron
Base modification
What enzyme is responsible for 3’ CCA addition?
tRNA nucleotidyltransferase
What are the sizes of the prokaryotic ribosome subunits?
50s (large)=23s +5s
30s (small)=16s
What are the sizes of the eukaryotic ribosome subunits?
60s (large)=28s+5.8s+5s
40s (small)=18s
How are prokaryotic rRNA synthesized?
Each precursor transcript contains one copy of each rRNA, resulting in 30s rRNA
How are eukaryotic rRNA synthesized?
The precursor transcript contains several hundred tandem repeats that must be processed
What transcribes the eukaryotic rRNA (besides 5s)
RNA Pol I, results in 45s precursor that contains one of each rRNA
What transcribes the eukaryotic 5s rRNA?
RNA Pol III
Where are eukaryotic rRNA assembled?
The nucleolus
