Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
124 Cards in this Set
- Front
- Back
|
Euk Ribosome Subunits and total |
60S + 40S = 80 S |
|
|
Prok Ribosome subunits and total |
50S + 30S = 70S |
|
|
ribosomes have catalytic activity in what type of RNA |
rRNA |
|
|
What accessory proteins are required for initiations of translation |
IF, eIF |
|
|
what accessory proteins are required for elongation of translation |
EF and eEF |
|
|
what accessory proteins are required for termination of translation |
RF, eRF |
|
|
how many possibilities arise from the 3-nt codon |
64 |
|
|
what are the only amino acids that have a single code? |
Met (AUG) Trp (UGG) |
|
|
what is considered the "21st aa" |
selenocysteine |
|
|
what is one example of "non-universal" genetic code (specific molecule) |
selenocysteine |
|
|
missense mutation |
coding for a different amino acid |
|
|
nonsense mutation |
coding for a termination codon |
|
|
silent mutation |
no change |
|
|
what is an example of programmed ribosomal frameshift |
gagpol polysome |
|
|
what is the normal ratio of gag : gagpol |
20:1 |
|
|
2 reasons why programmed ribosomal frameshift is so odd |
1. usually the other two reading frames contain no useful information 2.usually no punctuation until stop codon is reached |
|
|
what is RNA editing? |
processes that covalently change the identity or positioning of RNA bases after synthesis |
|
|
example of RNA editing and resulting proteins |
deanimation of cytosine converts C to U which changes glutamine codon to termination codon; apoB-100 in liver, apoB-48 in intestine |
|
|
General strategy for protein biosynthesis |
1. activation of amino acids (tRNA charging) 2. initiation (RL) 3.elongation 4. termination and release 5. folding and post-translational processing |
|
|
how many tRNAs for each amino acid? |
at least one |
|
|
how long are tRNAs generally |
about 100 nts |
|
|
what type of bonding accounts for the cloverleaf-like structure of tRNA |
H-bonding |
|
|
what are the two arms of the tRNA |
amino acid arm and the anticodon arm |
|
|
in what direction does the anticodon READ the mRNA |
5' - 3' |
|
|
reading a tRNA 5' - 3', which arm is on the left? |
D arm |
|
|
reading a tRNA 5' - 3', which arm is on the right? |
T(psi)C arm |
|
|
which arm is the CCA added to |
amino acid arm (3') |
|
|
which arm is the wobble position on? |
the anticodon arm |
|
|
technically how many tRNAs do you need to code all the amino acids |
32 |
|
|
what are the three classes of codon:anticodon interactoins |
1c/ac 2c/ac 3c/ac |
|
|
what determines how many codons recognized per anticodon |
the base in the 5' position in the anticodon |
|
|
if there is a C or an A in the 5' anticodon position |
1:1 codon:anticodon |
|
|
what is unusual about G pairing in RNA |
G can base pair with U |
|
|
what is the only place where G can pair with U? |
the 3' position of the codon |
|
|
why is it that G can pair with U in RNA? |
only here is there enough room in the molecule to allow for noncannonical basepairing of G and U |
|
|
what can anticodon 5' U pair with |
3' A or G |
|
|
what can anticodon 5' G pair with |
3' C or U |
|
|
what is the first thing that has to happen in the process of allowing an anticodon to recognize three codons? |
guanine has to be deaminated to inosine |
|
|
what can inosine form hydrogen bonds with |
AUC |
|
|
anticodon arm function |
recognizes mRNA codon by base-pair complimentarity |
|
|
amino acid arm (2 facts) |
always ends with CCA (3'); site of amino acid charging |
|
|
the first base of the mRNA codon (5-3) pairs with the |
third base of the tRNA antibodon (5-3) |
|
|
wobble specifies |
the rate of protein synthesis |
|
|
what are responsible for charging tRNAs with amino acids |
aminoacyl-tRNA synthetases |
|
|
where does the aa-tRNA synthetase bond the aa |
to the 3' end of the tRNA |
|
|
what enhances the fidelity of aa-tRNA assembly? |
enzymatic proofreading |
|
|
generally 1 aa-tRNA synthetase per |
amino acid |
|
|
is the work of aa-tRNA synthetase ATP dependent or independent |
dependent |
|
|
what base is paired to the amino acyl group? (in charging) |
adenine! (cca) |
|
|
50s subunit of ribosome contains |
23s and 5s rRNAs and 36 proteins |
|
|
30s ribosomal subunit contains |
16s rRNA and 21 proteins |
|
|
in a bacterial ribosome, where does the codon:anticodon recognition and aa-tRNA binding occur |
30S/50S interface |
|
|
in bacterial ribosomes, peptidyl transfer occurs in the |
50S subunit |
|
|
which subunit are the A and P site in |
the large subunit |
|
|
A-site: definition and location |
aminoacyl-tRNA site; interface between 50S and 30S |
|
|
P-site: definition and location |
peptidyl-tRNA site; interface between 30S and 50S subunits |
|
|
E site: definition and location |
exit site; largely within 50S subunit |
|
|
peptidyl transferase center: definition and location |
deep in 50S subunit; where 3' ends of end of P site tRNA and A site-tRNA are brought into close proximity; where |
|
|
what are the two translation factors in initiation of prokaryotic translation |
IF1 and IF-3 |
|
|
where do IF-1 and IF-3 bind? |
IF-1 binds to the A site; IF-3 binds elsewhere on the small subunit |
|
|
___ is all you need to initiate translation in a prokaryote |
the small ribosomal subunit (30s) |
|
|
which side of the mRNA is the initiation site on? |
either side, provided the initiation sequence context |
|
|
what is over AUG during initiaiton of translation |
the empty P site |
|
|
what is complementary to the shine-dalgarno sequence? |
the 3' end of the 16s rRNA of the small subunit |
|
|
what do you need in addition to the initiation codon to initiate translation in proks |
the shine-dalgarno sequence |
|
|
where is the shine-dalgarno sequence relative to the initiation codon? |
a few nucleotides upstream |
|
|
what does the IF-2-GTP complex do |
facilitates the binding of fMET-tRNA to the 30S subunit |
|
|
what happens after the binding of fmet-trna and the recognition of AUG |
complex joined by 50s subunit |
|
|
what happens prior to the release of the IFs from the complex? |
GTP-IF-2 hydrolyzed to GDP + Pi |
|
|
what is left when the IFs (1,2,3) are released |
the initiation complex (70s) |
|
|
at what point is the prokaroytic ribosome committed to elongation |
when the IFs dissociate and the 70s initiation complex has been formed. |
|
|
where is the shin-dalgarno sequence in euks |
there is none! |
|
|
what is the 43S complex made of |
in euks, cap-binding complex recruits 40S subunit |
|
|
what does the 43S complex do? |
scans the mRNA (5-3)until it reaches the initiation site |
|
|
in euks, what permits the recruitment of tRNAmet? |
43S recognition of initiation site |
|
|
when does the 60S subunit join? |
following the recruitment of the complex containing tRNAmet |
|
|
what is one major exception to the general pattern of initiation in euks |
IRESes - internal ribosome entry sites -- translation may initiate internallly |
|
|
the mRNA 5' cap is recognized by |
eIF4E |
|
|
the polyA tail is bound by the |
cytoplasmic polyA-binding protein (Pab1p) |
|
|
eIf4E and Pab1p are linked through |
eIF4G |
|
|
eIF4G links |
Pab1p and eIF4E |
|
|
what does eIF4G have with it |
the 40s subunit |
|
|
3 stages of prok elongation |
1. aa-tRNA recruitment 2. peptide bond formation 3. translocation |
|
|
what brings the aminoacylated tRNA to the ribosome A site |
EF-Tu-GTP |
|
|
who checks the codon-anticodon pairing in proks |
EF-Tu |
|
|
who recycles the EF-Tu GDP to its GTP state |
EF-Ts |
|
|
at what point is the tRNA "stuck" in the A site (prok) |
once the GTP is hydrolyzed (by EF-Tu) |
|
|
the nucleophilic attach during peptidyl transfer |
amide group of A-site amino acid attacks carbonyl group of P-site amino acid |
|
|
"net effect" of peptidy transfer step |
transfer of cargo from P-site to A-site a |
|
|
at the end of the first peptide bond formation step, what do you have in the p-site (proks) |
a deacylated tRNA-fMet |
|
|
translocation |
movement of ribosome 3 nts/1 codon toward the 3' end of the mRNA |
|
|
what fuels translocation |
GTP hydrolysis by the protein EF-G |
|
|
what does EF-G do? |
hydrolizes GTP to fuel translocation |
|
|
translation is completed when (broadly) |
any one of the three termination codons enters the A site |
|
|
what binds to the stop codon in the A site? |
RF factor |
|
|
what three things does the release factor signal the ribosome to do? |
1. hydrolyze the terminal peptidyl-tRNA bond 2. release the polypeptide and the tRNA 3. dissociate the ribosomal subunits |
|
|
what is a polysome? |
clusters of ribosomes on a single mRNA |
|
|
where does mRNA processing happen in prokaryotes |
mRNA is not processed in prokaryotes |
|
|
in proks, direction of translation and transcription is |
the same |
|
|
polycistronic - definition and prok/euk |
more than one unique protein per mRNA; prokaryotes |
|
|
where does transcription occur for euks |
nucleus |
|
|
where does translation occur for euks |
cytoplasm |
|
|
who lives longer: euk mRNA or prok mRNA |
euk mRNA |
|
|
what is the major feature that allows prokaryotes to be polycistronic |
multiple initiation sites via shine-dalgano |
|
|
what are two methods of nonsense suppresion |
1. misplaced termination codon resulting in new amino-acid codon 2. tRNA gene that recognizes tRNA gene but inserts an amino acid at that position |
|
|
what is a suppressor tRNA |
recognizes stop codon but changes identity of the anticodon loop thus inserts an amino acid at that position |
|
|
suppressor tRNAs are usually |
duplicate genes of normal tRNAs |
|
|
Puromycin |
P+E. causes premature chain termination by acting as an analog of aminoacyl tRNA. Cannot translocate which promotes peptide dossociation from the ribosome. |
|
|
puromycin mimics |
incoming aminoacyl-tRNA |
|
|
what is the major thing that puromycin cannot do |
translocation |
|
|
does puromycin make codon anti-codon contact? |
no; only resembles the 3' end of the aa-trna |
|
|
with puromycin, where does the existing polypeptide go? |
gets transferred to the puromycin; dissociates from the ribosome. |
|
|
tetracyclines |
(P) blocks the A site on the 30S subunit and inhibits binding of aa-tRNA |
|
|
do tetracyclines recognize 30s or 40s? |
30s (therefore specific for proks) |
|
|
Erythromycin |
(P) bind 50S subunit and inhibits peptidyl transfer and translocation |
|
|
Chloramphenicol |
Binds 50S subunit and inhibits peptidyl transfer |
|
|
Cycloheximide |
(E) binds 60S subunit and inhibits peptidyl transfer |
|
|
streptomycin |
binds 30S subunit, inhibits initiation and causes misreading of mRNAs (aminoglycoside antibiotic) |
|
|
what is an example of an aminoglycoside antibiotic |
streptomycin |
|
|
diptheria toxin |
inactivates eukaryotic eEF2 |
|
|
ricin |
inactivates the 60s subunit of the eukaryotic ribosome (via cleavage) |
|
|
in the presence of the diptheria toxin you will not be able to |
elongate new proteins (eukaryotes) |
|
|
translation inhibitors: prokaryotes |
puromycin, tetracyclines, erythromycin, chloramphenicols, streptomycin |
|
|
translation inhibitors: eukaryotes |
antibiotics: puromycin, cycloheximide toxins: diptheria, ricin |
