Lecture 7 fr

codons

3 letter genetic code (non overlapping)

reading frame

each potential starting point for interpreting 3 letter code

genetic code is ___. In any organism each codon corresponds to only one aa

unambiguous

__ multiple codons for most aa

multiple codons

code is __ and synonymous codons specify the same amino acid

degenerate

termination (stop codons)

UAA UGA UAG

initiation codon

methionine codon (AUG) also specifies initiation site for protein syn

tRNA interprets

genetic code

each tRNA recognize at least one

codon

tRNA have a __ type secondary structure with several loops or arms

cloverleaf

tRNA has an ___ and four arms

acceptor stem

accepted stem

aa covalently attached to tRNA at 3’ end

anticodon arm

anticodon binding to a complementary codon in mRNA

tRNA molecules named for ___ they carry

amino acid

base pairing follows rules of

Watson crick

wobble allows tRNA molecules to recognize

Morse than one Codon

isoacceptor tRNA

diff tRNA bind the same amino acids

bacteria have__diff tRNA and eukaryotes have up to __ diff tRNA

pro- 30-60

euk-80

aminoacyl tRNA

aa covalently attached 3’ end of tRNA

The activation of an amino acid by aminoacyl-tRNA synthetase needs

ATP

some aa-tRNA synthetases can

proofread

ribosome complex moves in __ along template mRNA

5’ → 3’

polypeptide synthesized in ___ direction

N→ C

E. coli 70s composed of

30s and a 50s

eukaryotes 80s composed of

60s and a 40s

translation complex assembled at the beginning of the

mRNA coding sequence

imitator tRNA recognizes

Initiation codons

Bacteria initiator tRNA

N-formylmwthionyl-tRNA

Eukaryotes initiator tRNA

Methionyl-tRNA

Prokaryotes , the 30s ribosome binds to a region of the mRNA or the ___ sequence

shine dalgarno sequence

Initiation factors are required to form a complex

pro factors are:

Euk factors are

pro- IF

eu-eIFs

Which site is initiator tRNA

P site is where initiator tRNA is

Site A is ready to receive a

aminoacyl-tRNA

elongation is a 3 step cycle

1) positioning the correct aa-tRNA in the site A

2) formation of a peptide bond

3) shifting mRNA by one codon

a ternary complex of EF-Tu-GTP-aa-tRNA binds in the ribosomal __ site

A site

peptidyl transferase activity contained in ___ ribosomal subunit

Large

Catalytic activity from __S rRNA (an RNA-catalyzed rxn)

23

translocation step

new peptidyl-tRNA moved from A site to P site while the mRNA shifts by one codon

deaminoacylated tRNA shifted from site to the __ site

P to the E

EF-1a

dock the aa-tRNA into A site

EF-1B

Recycle EF-1a

EF-2

carries out translocation

3 termination codons in A site

UGA UAG UAA

amino acid activation : two ~p bonds

ATP → AMP + 2Pi

chain elongation two ~P bonds

2 GTP → 2 GDP + 2Pi

puromycin 3’ end aminoacyl-tRNA enter the __ site of a ribosome

A site

Ribosomal protein encode one ribosomal protein that ___ translation binding near ____ codon of the mRNA

inhibits and initiation

inhibition of protein syn. By

phosphorylation of eIF-2

cotranslational

before the polypeptide chain is complete

posttranslational

after the polypeptide chain is complete

secreted proteins are synthesized by ribosomes surface of the

endoplasmic reticulum

signal peptide

present on N-terminus that signals the protein to cross a membrane

A site

where charged tRNA enter the ribosome

P site

Holds onto the growing peptide chain

E site

Where tRNAs are ejected from the ribosome after their amino acid has been incorporated into the growing peptide chain

T-arm

aids entry into the ribosome

D-arm

ensures correct amino acid charging

Pr, Eu, IF, EF

Pr- prokaryote

Eu- eukaryote

imitating factors

Aminoacyl-tRNA binds to A site

GTP

EF-Tu and ETFS (Pr)

eEF-1 (Eu)

shiva toxic inhibits

(cuts 28s rRNA)

Peptide bond forms in the A site

peptidyl transferase in a large subunit

translocation of ribosome 3 nucleotides along the mRNA

GTP

EF-G (Pr)

eEF-2 (Eu)→ G protein

pseudomonas and diphtheria toxin inhibit ( ADP-ribosylation) of eEF-2

__ high energy bond used per peptide bond

4

Aminoglycosides

streptomycin

gentamycin

a1-antisepsis needs a ___ to fold in the ER

chaperone

fibroblasts

common presence of inclusion bodies in fibroblasts

I-cell disease will not

large inclusions from molecules should’ve been degraded by the lysosome and is just sitting there

coarse facial features

add joint pain and psychomotor retardation in young child

in the Golgi other sugars can be added

O-glycosylation. Sugar added to -OH of see the post translational modification

translation begins in

cytoplasm

signal sequence causes ___ to attach to ER

ribosome

peptide is threated through the membrane into the ____ lumen

ER

A sugar is added to

Nitrogen of asparagine

signal peptide removes ___

signal sequence

translation continues on

RER

Co translational while protein is being made ___ is added

sugar

protein then goes into __ and secreted

Golgi

Glycosylation in __ (continues in Golgi)

ER

Proper folding is required in ER for transfer of protein to ___

Golgi

O-linked in glycosylation in the

Golgi

I-cell disease

defect in phosphotransferase