1 / 27

VALGUSÜNTEESI INITSIATSIOON EUBAKTERITES

VALGUSÜNTEESI INITSIATSIOON EUBAKTERITES. INITSIATSIOON. 30S subühik mRNA Initsiator-tRNA fMet-tRNA fMet Initiation factor 2 + GTP Initiation factor 1 Initiation factor 3 50S subühik. 30S subühik. Seonduma mRNAga Vahendada initsiatoorset tRNA seondumist mRNAga

tannar
Download Presentation

VALGUSÜNTEESI INITSIATSIOON EUBAKTERITES

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. VALGUSÜNTEESI INITSIATSIOON EUBAKTERITES

  2. INITSIATSIOON • 30S subühik • mRNA • Initsiator-tRNA fMet-tRNAfMet • Initiation factor 2 + GTP • Initiation factor 1 • Initiation factor 3 • 50S subühik

  3. 30S subühik • Seonduma mRNAga • Vahendada initsiatoorset tRNA seondumist mRNAga • Vahendada 50S seondumist

  4. PEA KAEL PLATVORM KEHA

  5. anti Shine-Dalgarno PEA KAEL PLATVORM KEHA

  6. mRNA • Codes for right positioning of protein synthesis start site into 30S

  7. mRNA AUG 90% GUG 8% UUG 1% AUU 0.1% aSD: AUUCCUCCACU UAAGGAGGUGA A/U rikas SPACING DB START CODON 5’ 3’ ENHANCER SD 6-8 nt SECONDARY STRUCTURE

  8. 30S mRNA

  9. fMet-tRNAfMet • Initiate protein synthesis • Binds to mRNA start codon in P-site on the ribosome

  10. fMet-tRNAfMet • Mismatch at the end of acceptor stem • Three conserved G:C base pairs in the anticodon stem • Formylmethionine

  11. fMet-tRNAfMet • Methionyl-tRNAfMet formyl transferase • Addition of the formyl group to the Met-NH2 creates a block resembling a peptidyl group

  12. fMet-tRNAfMet

  13. INITIATION FACTOR 2 GTP • Stimulation of fMet-tRNAfMet binding to the P site of the ribosome • IF2 favors the association of bacterial ribosomal subunits • Ensures that the initiation complex is formed with only initiator tRNA

  14. INITIATION FACTOR 2 GTP • G domain binds GTP or GDP • C-terminal domain contains all molecular determinants necessary and sufficient for the recognition and binding of fMet-tRNAfMet • IF2 in the GTP form stabilizes the binding of initiator tRNA to the 30S subunit.

  15. INITIATION FACTOR 1 • IF1 prevents premature binding of aminoacyl tRNA • IF1 stimulates IF-2 dependent fMet-tRNAfMet binding to 30S • IF1 modulates the interaction of IF2 with the 30S ribosomal subunit.

  16. INITIATION FACTOR 1 • The smallest IF • IF1 sterically blocks tRNA binding to the A site • IF1 causes movements of of the domains of the 30S with respect to each other, exponate aSD sequence

  17. INITATION FACTOR 3 • IF3 antagonizes the association of 30S and 50S subunits • Accelerates codon-anticodon interaction • Promotes translation of natural mRNA • Promotes dissociation of pseudo-initiation complexes • Promotes binding of other IF • Antagonizes mRNA with weak TIR (IF3-AUU start codon)

  18. INITATION FACTOR 3 • Consists of 192 residues • Can adopt a large variety of conformations • IF3 binding is not affected by the other two factors

  19. INITIATION FACTORS

  20. TRANSLATION INITIATION

  21. TRANSLATION INITIATION

  22. TRANSLATION INITIATION CONTROLL

  23. TRANSLATION INITIATION CONTROLL TRANSLATIONAL COUPLING • L11 - L1 cacggggagcctctcagaggcgttattacccaacttgaggaatttataatg.......gatgactcgctccatcgaaggtactgcacgttccatgggcctggtagtggaggactaagaaatg • L14 – L24 – L5 –... tatggggatttttaacgacctgattttcgggtctcagtagtagttgacattagcggagcactaaaatg...tagtgagaagttcatgcaaattatctctctggcaccagaagtactctaaggagcgaatcatg... aaaaagtccgtttcttcaagtctaacagcgaaactatcaagtaa ttggagtagtacgatg...

  24. TRANSLATION INITIATION CONTROLL • When synthesized in excess over rRNAs, primary rRNA-binding proteins interact with their mRNA and inhibit translation of their own genes and the other genes in their operon. The similarities observed between mRNA and rRNA targets for a number of E.coli ribosomal proteins, sustain the mechanism based on mimicry and competition.

  25. TRANSLATION INITIATION CONTROLL

  26. TRANSLATION INITIATION CONTROLL

  27. TRANSLATION INITIATION

More Related