Life of Proteins Flashcards
monocistronic
one ORF per mRNA
polycistronic
mRNA codes several ORFs
eukaryotic mRNA is ____, prokaryotic mRNA is _____
monocistronic
polycistronic
where do tRNA anneal to 3-base codons on the mRNA
3-base anticodon region
what do tRNAs have at acceptor terminus
amino acid
how many possible codon sequences are there
64
wobble hydpotsis
position of of the anticodon is flexible and can wobble to pair with different nucletodies in the 3rd position of the codon
what does tRNA have that isn’t found in DNA or mRNA
inosine
how are tRNA molcules linked to amin oacid
aminoacyl-tRNA synthases
how many aminoacyl tRNA synthetases are there
20
where does translation take place
cytosol on ribosomes
how many subunits do ribosomes have
2
how many RNA molecules are found in ribosomal subunitns
1-3
function of cytoplasmic ribosomes
synthesis of the bulk of proteins
function of mitochondrial ribosomes
protein sythesis inside of mitochondria
where are ribosomal subunits syntehsied
cytosol
intiation of translation requires the correct assumbly of waht
- small ribosomal subunit
- mRNA
- tRNA that binds the first codon
what happens once the small subunit is laoded with tRNA and mRNA
binds to large subunit to conclude insitation phase
first step of intiation
elF2a activated by binding GTP
what does elF2a-GTP do
binds intiator methionine-tRNA met to form ternary compelx
what does ternay complex do
bind small ribosomal suunit
what happens to the small ribosomal subunit
mRNA binds to it, forming pre-initiation complex
what does pre-initaition compelx do
assembles into initation complex by binding large ribosomal subunit
how does elongation phase starte
initation methionine tRNA met binds to P site of ribosome
what happens after initatior methionine tRNA met binds to P site
second aminoactyl-tRNA placed into A site which requies EF-1
what happens after the aminoacyl-tRNA is placed on the A site
peptidyl bond formed btwn 1st and 2nd amino acid
what happens after the peptidyl bond forms
ribosome moves one codon further on mRNA with help from EF-2. now mRNA-peptidyl complex is in P site and A site is empty. uncharged tRNA levels through E site
how does termination start
stop codon reaches A site of ribosome
what happens after ribosome reaches A site
eRF pairs with stop codon
what happens after eRF pairs with stop codon
eRF bound GTP is hydrolyzes and peptides is released from P site
how does streptomycin work
binds to small subunit and inhibitis initiation
how does neomycin and gentamicin work
bind to ribosomes and cause mistranslation of codonds
how does tetracycline work
block A site, prevents tRNA binding
how does chloramphenicol work
prevent peptidyl bond formation
how does riicin work
removes adenine bases from various positions of the rRNA in the alrge subunit
how do you regulate transctation
prevent recognitino of start codon
regulat acitivity of initaiton factors
how do chaperones work
binding to hydrophobic regions of the folding peptide
where are chaperons foudn
cytosol and ER
Charcot Marie Tooth Disease is caused by what
mutation in HSP gene
what happens to cells during the unfolded protein response
inhibit global protein translation
induce chaperone production
apoptosis
what does glycosylation do
changes the physical properties of proteins
where does glycosylation of proteins take place
begin in ER, continue into golig
reaction of glycosylation
glycosyltransferase transfers sugar from activiated sugar nucleotide to acceptor substrate
what are the glycosyltransferases specific for
- the sugar donor
- the acceptor molecule
- type of glycosidic bond formed
what happens during N linked glycosylation
an oligosaccharide molecule is added to tha mino group of an aspargine residue
steps of N linked glycosylation
1) synthesis of univeral oligosaccharide on dolichol phostate in ER
2) transfer of univeral oligosaccharide to nascent polypeptide chain
3) modification of univeral oligosaccharide in golgi
O-linked glycosylation
post translation event, only occurs on fully folded proteins. only occurs after protein has reached golgi
step of O link glycosylation
glycosyltransferases of goligi transfer N-acetyl-galactosamine to hydroxyl group of serine or threonine rediues on surface of protein
what is O linked glycosylation involved in
blood typing
how can proline be modified
hydroxylated to function in colalgen triple helix
