what is the start codon?
AUG = methionine
what are the stop codons?
UAA
UAG
UGA
what is the wobble base position?
3rd position
how is it that each tRNA can bind to more than one codon?
tRNA binds using either watson-crick binding or wobble base binding
wobble bases are made by modification using enzymes
allows the use of fewer tRNAs for the 64 codons
what is an some example of wobble base modification?
A ——> inosine
(by deamination)
- inosine can bind to A, U or C
how is an amino acid coupled to a tRNA during protein synthesis?
- AMP added to c-terminus of amino acid
- adenylated amino acid used to attach tRNA to amino acid - high energy ester linkage formed. aminoacyl-tRNA formed.
enzyme used = aminoacyl-tRNA synthetase
how does the correct amino acid pair with the correct tRNA?
amino acid has to fit into 2 different pockets in the synthetase (before and after AMP addition)
tRNA nucleotides in the acceptor stem, anticodon etc. fits into pockets in the synthetase
what is the function of the large ribosomal subunit?
catalyses polymerisation (of amino acids)
what is the function of the small ribosomal subunit?
facilitates amino acid/tRNA interaction
what is the function of EF-1 and how does it work?
- anticodon on tRNA binds to codon on mRNA
- EF-1 prevents peptidyl transferase from working -> causes delay allowing time for incorrectly bound tRNAs to fall off
- EF-1 hydrolyses GTP to GDP
- EF-1 dissociates from tRNA
DEFINE: ribozyme
an RNA that catalyses a reaction
how are eIFs involved in translation
- mRNA with a 5’ cap and 3’ poly A tail bound by eIF-4G and eIF-4E + forms a loop
- methionine tRNA and eIF-2 bound to small subunit
- complex binds to 5’ cap and associated eIFs
- complex scans mRNA to search for first AUG for tRNA to bind to
- methionine tRNA forms base pairs –> signals for release of eIF and binding of large subunit
- translation begins
what are release factors
- recognise stop codons
- look like charged tRNAs + enter A site –> facilitates dissociation of ribosome
what is a molten globule
protein initially folded into roughly the correct conformation with hydrophobic side chains put in the middle to achieve a lower energy state
what is misfolding
reaching low energy state creating an uphill battle to get to its properly folded state
hsp70
no atp required
binds to hydrophobic side chains on proteins to protect them from sticking together to give time to fold properly
hsp60
large chamber with hydrophobic amino acids on surface of entrance = recognises proteins with hydrophobic amino acids on their surface
misfolded proteins pulled into chamber and partially unfolded
groES cap seals protein inside to allow refolding . atp required.
what are protein aggregates?
cluster of proteins without a functional morphology
which diseases are associated with protein aggregates?
CJD
huntington’s disease
alzheimer’s disease
what are prions?
protein aggregates converting normal proteins into misfolded proteins
amyloid plaques formed = made up of cross-beta filaments
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111
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Lecture 18: RTKs23
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LECTURE 19: Insulin signalling21
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dna damage17
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cell adhesion32
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control of gene expression: rna24
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rna transcription15
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protein structure21
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chromosomes9
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dna replication15
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protein synthesis20
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identifying and analysing genes18
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vesicular transport28
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genome evolution4
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signalling via intracellular receptors19
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control of gene expression15
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protein interactions9
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recombinant technology8
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chromatin15
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protein trafficking10
