8/13/2019 Protein TL
1/1
!"#$%&' ) * +,#-&". /,0.120-"#.
TranslationComponents-mRNA-tRNA-ribosome-accessory
factors:initiation, elongation,release-polypeptide product
Synthetases highlyspecific for each aa linkaas to each tRNA
(ATPdependent). Readanticodon-activate by adenylation(aminoacyl
tRNA w aa-
AMP intermediate-zinc site-proofreading fxn
Initiation: Binding Sites-1 st codon 5+25,
AUG(methionine)-Shine-Delgarno: purine-rich5+10 compl. to 3 end
of16S rRNA-Kozak: 43S/48S5.ccAccAUGG.3 affectsquantity of protein
made
Initiation: Sequence-IF1, 3 bind to 30spreventing premature70S
formation-IF2 binds formylatedtRNAf and GTP,associates w mRNA;GTP
hydrolysis -> IF3release -> 70S-Shine/Delgarno-16Sinteraction
established-fmet-tRNA pairs w AUG-GTP hydrolysis (again
WTF) IF1,2 dissociation
Termination Normal tRNAs do notrecognize stop codonsUAA, UGA,
UAG RF1or 2 recognizes these,RF3 mediates theirinteraction w
ribosome.-RF Gly-Gly-Gln bindswater molecule-GTP dependent-RF
mediates ribosomaldissociation.
Post-TranscriptionalRNA editing-apoB100
CAA->UAAdeamination-get apoB48 instead-diff product in gut v
liv
(Prok) tmRNAFinish broken mRNA,target bad protein
fordegradation
Targeting Pathways:-post-translational-co-translational-SRPs and
signalsequences mediateattachment of ribosometo RER for completion
oftranslation
Secretory pathway (co-translational)-ribosome on RER
synthprotein, secrete into ER-out via vesicle to Golgi-through
Golgi out viasecretory vesicle-fusion w plasmamembrane
Post-translationtargeting-myristic acid andpalmitic acid
anchoringresidues surface assoc-farnesine lipid
rafts-mannose-6-PO4:lysosome-seq on myc TF forchaperone ->
nucleus-RAN GTP/GDP
Membrane boundProteins -7aa stop transfer signalstops extrusion
into ER-piece of membrane wprotein attached formsvesicle
Protein turnover °radation-Glycosylation patternstell
proteins where to goto get degraded-Abnormal glycosylation= disease
eg Tay-Sachs(inability to break downbranch chaingangliosides)
Ubiquitinylation -proteolysis can reveal sequences
forubiquitinylation-tag for proteolytic cmplex-E1 activation-E2
conjugation-E3 protein ligase-SUMOylation small
ubiquitin-likeprotein-RICIN has no exposed lysine
residues-Alzheimer, Parkinson, Huntington denatured protein
aggregation-PEST: gets ubid-26S Proteosome: lidded trashcan
2ary mRNA structure-cmyc, ferritin,transferrin,-myc, 3 exons,
loss of
E1 stem/loop can lead tooveractivation-ferritin : stem loop
IRE
protein bound in low-Feand blocks translation-transferrin :
aconitase,normally anabolicenzyme, under low Febinds mRNA
andinduces transferrinproduction
Significant EventsControlling Translation-polio virus: makes
aprotease to cut off the 5cap.
Antibiotic vs ribosome-puromycin , aa-tRNAanalog, blocks A
site,forms peptide bond,premature termination-streptomycin
blocksfmet-tRNA binding-erythromycin binds to50S blocks
translocation
Elongation -EPA sites-aa-tRNA w EF-Tu into Asite, GTP hydrolysis
if ok-spontaneous formationof peptide bond i/o ester-translocation
ofmRNA/tRNA med by EF-G (translocase) empties the A site, alsovia
GTP
Abx resistance -mutations causevariations in 23S rRNA,abx eg
clindamycincannot bind to 50S exittunnel.
Ricin and shigatoxin -RIP: ribosomalinactivation protein Achain
has adenosinedepurination activity,removes a single rRNAbase, cant
recognizeEF, no protein synthesis
Hormone-receptorinteractionsHormones bind tosoluble receptors
with aDNA binding and aligand binding domain DNA domain has 9
cyszinc finger; ! helix thatinteracts w majorgroove; binds as
dimerto ERE. Needcoactivators orcorepressors to work.
PKA, CRE, CREB
