protein Flashcards
amino-tRNA Synthetase
enzyme required to catalyze the attachment of an amino acid to tRNA
attaches a specific AA to the 3’ acceptor stem of the congate tRNA molecule
“charges” tRNA and is coupled to ATP hydrolysis
Class 1: rossmann nucleotide, charges tRNA on 2’ OH
Class 2: antiparallel beta strand, charges tRNA on 3’ OH
aminoacylation reaction: thermodynamically favored (ATP driven)
carboxyl group on AA attacks ATP
then charge tRNA
isoacceptor tRNAs
different tRNAs for the same AA that bind alternate codons
recognized by a single aminoacyl-tRNA synthetase
have an invariant residue at recognition positions on the acceptor stems
2 proofreading steps: active site & editing site
isoacceptor tRNAs
different tRNAs for the same AA that bind alternate codons
recognized by a single aminoacyl-tRNA synthetase
have an invariant residue at recognition positions on the acceptor stems
2 proofreading steps: active site & editing site
Active site: proofreading site, allows certain class/size
editing site: removes incorrect AA
wobble bp
first two nucleotides the same, I pairs with AUC
protein synthesis initiation
AUG is start codon
initiator tRNA is formylated to produce fMet-tRNA after aminoacylation
initiator tRNA binds to P (peptidyl) site
termination
terminated by STOP codons
release factor binds to ribosome in place of charged tRNA
polypeptide chain released
GTP is hydrolyzed by release factors and disassemble complex
elongation
second tRNA binds A site
rRNA helps peptide bond formation
peptide transferred to P site
uncharged tRNA leaves from E site
prokaryotic initiation
30S & 50S subunit for 70S ribosome
Shine Dalgarno sequence appears upstream from AUG
3 initiation factors
eukaryotic initation
used 40S and 60S subunit to form 80S ribosome
multiple elongation factors & GTP & ATP required
eukaryotic initation
used 40S and 60S subunit to form 80S ribosome
multiple elongation factors & GTP & ATP required
specific RNA sequence required at 5’ and 3’ end
Peptidyl Transferase Reaction
Amino group of the amino acid attached to the 3′ terminus of the tRNA in the A site attacks the carbonyl carbon of the peptidyl-tRNA in the P site
chloramphenicol
bind to 50S subunit and prevent peptide bond formation
erythromycio
binds to 50S subunit and prevents translocation
tetracyclines
prevent tRNA binding to A site of ribosome
strepromycin
alter the structure of the 30S subunit, causing errors in translation
puromycin
bind to A site of 50S subunit
peptidyl transferase reaction attaches peptide to puromycin
palmitoylation
attachment of C=O +14 carbon lipid to cerine
myristoylation
attachment of C=O + 12 carbon lipid to terminal G
prenylation
attachment of unsaturated lipid to cyctein
phosphorylation
attachment of phosphate group to OH
(S, T, Y)
methylation
attachment of methyl group to lysine
acetylation
attachment of C+O CH3 (aceytl) to lysine
ubiquitination
add C=OUb to lysine
glycation
Oligosaccharide attachment can be O linked or N linked
glycan assembled attached to membrane
glycosyltransferase attached glycan to protein in ER lumen
