1. Lizabeth Allison Ch:14 Waever Ch 17, 18, 19
Translation
Lizabeth Allison Ch:14
Waever Ch 17, 18, 19

2. Ribosome Synthesis of protein Found in cytoplasm
Free or attached to ER
Two subunits
70S in prokaryotes and 80 S in eukaryotes

15. tRNA charging
CCA appended post transcriptionally

16. Aminoacyl tRNA synthetase

18. Proof reading activity of aminoacyl tRNA synthetase
Extensive contacts with tRNA and amino acid
Hydrolyzing activity removes wrong amino acid

19. Initiation

20. Charging of tRNA (prokaryotes formyl-Met)
Formation of ternary complex (aa-tRNA, GTP, initiation factor)
Loading on small subunit
Scanning start codon (Shine-Delgarno in prokaryotes cap and tail in eukaryotes)
Assembly of large subunit

23. Initiation Cap-independent initiation. Internal ribosome
entry site (IRES) trans-acting factors (ITAFs,
eIF4A (dark blue) is an RNA-
dependent ATPase and RNA helicase

24. Elongation
Decoding
Transpeptidation
Translocation

27. Figure 14. 12 Incorporation of selenocysteine at a stop codon
Figure Incorporation of selenocysteine at a stop codon. Insertion of selenocysteine at UGA codons requires a selenocysteine insertion sequence (SECIS). (A) In eubacteria, elongation factor SelB binds both the SECIS located immediately 3′ to the UGA and tRNASel . (B) In eukaryotes, the elongation factor requires an adaptor, SBP2, and SECIS is located in the 3′ untranslated region.

29. Figure Cotranslation translocation pathway from the ribosome to the endoplasmic reticulum lumen

30. Termination
The termination of translation occurs in response to the presence of a stop codon (UAG, UAA, or UGA) in the ribosomal A site
The end result of this process is the release of the completed polypeptide following hydrolysis of the ester bond linking the polypeptide to the P-site tRNA
Release factors

32. Trasnlational and post translational control
Phosphorylation of eIF2a blocks ternary complex formation
Many different types of stress, such as hypoxia, viral infection, amino acid starvation, and heat shock repress translation by triggering the phosphorylation of the α-subunit of eIF2 at residue Ser51
This inhibits the exchange of GDP for GTP on the eIF2 complex, which is catalyzed by eIF2B, and thereby prevents formation of the ternary complex

34. Heme availability controls globin synthesis (eIF2 kinase (heme-regulated inhibitor))

35. Interferon protect against viral infections
Interferons are cytokines that are secreted by virus-infected vertebrate cells
On binding to surface receptors of other cells, interferons convert them to an antiviral state,which inhibits the replication of a wide variety of RNA and DNA viruses

37. Interferons also induce the synthesis of (2,5)- oligoadenylate synthetase (2,5A synthetase). In the pres ence of dsRNA, this enzyme catalyzes the synthesis from ATP of the unusual oligonucleotide pppA(2p5A)n where

38. Regulation of eIF4 (binds 5’ cap)
When mammalian cells are treated with hormones, cytokines, mitogens (substances that induce mitosis), and/or growth factors, Ser 209 of human eIF4E is phosphorylated via a Ras activated MAP kinase cascade
Thereby increasing eIF4E’s affinity for capped mRNA and hence stimulating translational initiation

39. mRNA masking
unfertilized egg contains large quantities of mRNA that is “masked” by associated proteins to form ribonucleoprotein particles, thereby preventing the mRNAs’ association with the ribosomes
On fertilization, this mRNA is “unmasked” in a controlled fashion, quite possibly by the dephosphorylation of the associated proteins, and commences directing protein synthesis

40. cytoplasmic polyadenylation element (CPE), which has the consensus sequence UUUUUAU.The CPE is recognized by CPE-binding pro- tein (CPEB), which contains two RNA recognition motifs (RRMs) as well as a zinc finger motif

43. Post translational modifications
Proteolytic cleavage
Digestive enzymes
Collagen
Insulin
Removal of signal peptides
Polyproteins

44. Post translational modifications

45. Post translational modifications
Covalent modification
Acetylation, alkylation
Collagen hydroxylation (Pro, Lys)
Phosphorylation
Lipidylation
Glycosylation

46. Post translational modifications
Protein splicing (intein and extein)