tRNA and aminoacyl tRNA synthetases Flashcards
-understand how to use the genetic code table -understand tRNA structure -understand the wobble hypothesis and what it means for base-pairing -understand how the genetic code is embedded in aaRS enzymes -understand the biochemistry of aaRS enzymes -understand proofreading by aaRS enzymes
how many nucleotides long is tRNA?
75-90 nucleotides long
the ___ end of tRNA is linked to an ____ ____, which is specifically attached to the _____ base
3’
amino acid
adenine
name a unique feature about the structure of tRNA
it contains many modified bases, specifically in the arms of tRNA
true or false: all tRNAs have a similar structure because they need to bind to a particular part in ribosomes
true
the ___ position of the codon is the ___ position of the anticodon, and at that position there will be flexibility - this is called “_____”
3rd
1st
wobble
what does “I” stand for in tRNA?
inosine
what is unique about inosine?
it has expanded base pairing capabilities (can bind to A, U, C)
inosine is ______ adenosine
deaminated
the _______ is not involved in checking to see if the correct amino acid is attached to tRNA
ribosome
____ ________ are involved in attaching the appropriate ____ ___ onto the corresponding tRNA
tRNA synthetases
amino acid
what’s the short term for aminoacyl tRNA synthetase?
aaRS
what is a charged tRNA?
tRNA with an amino acid attached to it
during the activation of an amino acid, how many ATPs are used?
2
the ____ ___ does a nucleophilic attack on the __ phosphate group of ATP, thus releasing ______
amino acid
alpha
pyrophosphate
aminoacyl-AMP is referred to as a _____ _______ because it has both a phosphoester bond and an ester bond
mixed anhydride
true or false: there is a class I aminoacyl-tRNA synthetase and class II aminoacyl-tRNA synthetase
true
for class I aaRS, the __ OH attacks the carbon (on the ester) of the amino acid, and releases ___
2’
AMP
for class II aaRS, the ___ OH attacks the carbon (on the ester) of the amino acid and releases __
3’
AMP
in both class I and class II aaRS, the amino acid ends up on the ___ position of adenine and attached to _____
3’
tRNA
the amino acid on the 2’ position moves to the 3’ position via a __________ reaction
transesterification
how are tRNA synthetases similar to DNA polymerase I?
if the incorrect amino acid is added on, then it flops over to the editing site where it will be removed (DNA polymerase 3’ to 5’ exonuclease does the same thing but w/ nucleotides)
what are the tradeoffs for accuracy in translation?
energy and time
true or false: some aaRS do not proofread at all
true
the aaRS that puts the amino acid ______ on does not have any proofreading activity…why not?
tyrosine
because the catalytic site for tyrosine is different in that tyrosine is bulky, and it has hydrogen bonding for the OH group (allowing for specificity against Phe)
