Flashcards in B2.053 Prework 1 Protein Translation Deck (30)
where do translation initiating complexes assemble?
7-methyl guanosine cap of mRNA
what is the function of the cap binding complex?
recruits small subunit of ribosome to mRNA
adaptor between the cap and ribosome
what is the name of the cap binding complex?
what 3 subunits make up eIF4F?
eIF4A eIF4G eIF4E
which subunit of the cap binding complex is limiting?
discuss the function of each subunit of eIF4F complex
eIF4E = binds to m7G-CAP, limiting subunit
eIF4G = scaffold
eIF4A = helicase
what is the initial recognition event that sets translation into motion?
cap complex eIF4F binds to mRNA cap
what is the second initiation event?
eIF2 loads methionyl-tRNA onto small ribosomal subunit
what % of translation starts w methionine?
which factors mediate the interaction between eIF4F and the small ribosomal subunit?
what does the small ribosomal subunit do after binding to eIF4F?
scans along mRNA until the recognition of the start codon AUG
what happens once the start codon is encountered by the small ribosomal subunit?
the initiation factors are release and the large ribosomal subunit binds (elongation commences)
what is PABP?
poly A binding protein
interacts with polyA tail and cap binding complex
why is PABP useful?
drastically improves translation of mRNA
keeps ribosomes/eIFs near?
circularization of ribosome bound mRNA
how long is the polyA tail?
what makes up the 60S subunit?
what makes up the 40S subunit?
what are the 3 sites on the ribosome?
A site: aminoacyl
P site: peptidyl
E site: empty
what happens in the A site?
tRNA for the next codon enters
what happens in the P site?
site of the growing peptide chain attached to tRNA
how do toxins inhibit ribosome function?
rRNA N-glycosylase, cleaves N-glycosidic bond of adenine at position 432 in 28S rRNA
loss of protein synthesis results
which toxins inhibit rRNA function?
shiga toxin (bacteria)
ricin toxin (castor bean)
what factor is required for translocation/elongation?
how does EF2 work?
hydrolyzes 1 GTP per translocation to move the ribosome
what are diphtheria toxin and exotoxin A?
catalyze ADP ribosylation of EF2, blocking GTP hydrolysis
shuts down ALL translation
among the most toxic proteins that exist
what is EF1?
elongation factor 1
escorts next tRNA to the vacant A site
hydrolyzes one GTP per amino acid
what is important about the ester bond on the acceptor stem of a tRNA?
it is a high energy bond which is utilized in the formation of the peptide bond in protein synthesis
what catalyzes the peptide bond formation?
23S rRNA of the large ribosomal subunit is catalytic molecule
what happens following peptide bond formation?
the nascent peptide shifts from P to A site
ribosome translocates to the next codon, moving the nascent peptide back to the P site