RR11: Translation 1 Flashcards
(47 cards)
what removes the nuclear proteins associated with mRNA once it is on the cytoplasmic side?
helicase activity associated with cytoplasmic filaments on the cytoplasmic site
what are 2 proteins that bind to the mRNA once it is on the cytoplasmic side?
cap binding complex eIF4E
protein that binds to the poly A tail, PABPC (c for cytoplasmic)
what happens to PABPN?
sent back to the nucleus
what happens when RNA is decorated with all the important proteins?
ready to be translated
how do all 3 classes of RNAs play an essential role in translation?
tRNAs are required to bring in the AAs and read the codons on the mRNA
rRNAs are there for assembling the giant protein synthesis machinery that enables the complex to read the mRNA and summon the correct tRNAs and AAs
the mRNA is the sequence of codons
what proportion of the RNA in cells does rRNA make up?
transcribed at a very high rate, makes up 80% of the RNA in cells, by far the most abundant
what is the composition of the large ribosomal subunit in bacteria?
23S RNA+ 5S RNA + 31 proteins = 50S large subunit
what is the composition of the small ribosomal subunit in bacteria?
15S RNA+ 21 proteins = 30 S small subunit
what is the size of the bacterial ribosome?
70S
what is the composition of the large ribosomal subunit in eukaryotes?
28S rRNA+5.8S RNA+ 5SRNA+ 50 proteins = 60S large subunit
what is the composition of the small ribosomal subunit in eukaryotes?
18S rRNA + 33 proteins = 40S small subunit
what is the size of the eukaryotic ribosome?
80S
what is an important property of the rRNA?
across organisms sequence is highly similar, there are fluctuations
the secondary structures that those sequences generate are highly conserved in almost all organisms
forms a highly complex structure with many stem loops
the way in which RNA folds is related to its function
what shape does tRNA fold into?
an upside down L
where is the anticodon positioned on the tRNA?
at the top of the L
where will tRNA attack aminoacyl-tRNA synthethase?
at the extremity of the base, the 3’ end
what does aminoacyl tRNA synthethase do?
ensures that the appropriate AA is bound to a tRNA
what are the two important sites present on aminoacyl tRNA synthetase?
there is a substrate binding site on the enzyme, and then a site for the appropriate interaction with the correct tRNA that would encode for the particular amino acid
what ensures that the correct AA is linked to the tRNA?
interactions with the anticodon loop and sometimes other regions within the tRNA per se
how does aminoacyl tRNA synthetase create the bond between the AA and tRNA?
use ATP to link that amino acid to the 3’ end of the tRNA to generate a high energy ester bond
* This AA is now linked to that particular tRNA
what makes the genetic code degenerate?
a single aminoacyl tRNA synthétase can bind to more than one unique tRNA and a single tRNA can bind to more than one single codon
how come multiple codons can code for the same amino acid?
- When the ribosome is reading on a codon, it creates a very special environment
- The 3’ nucleotide of the codon and the 5’ nucleotide of the anticodon can sometimes interact in NON Watson crick base pairing manners, so there is a little bit of flexibility (wobble pairing)
what are some amino acids that are coded for by different codons?
leucine, serine, arginie
what are some amino acids coded for by only one codon?
tryptophan (UGG) and methionine (AUG)