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Group II Self-Splicing Introns

Group II Self-Splicing Introns. -pre-rRNA of fungal and plant mitochondria -majority of chloroplast introns -several classes -require Mg 2+ -no cofactor. Domain Structure of a Group II Intron. A. 5’ exon. 3’ exon. Chemistry of Group II Self-Splicing. 1st step. 2nd step. lariat.

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Group II Self-Splicing Introns

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  1. Group II Self-Splicing Introns -pre-rRNA of fungal and plant mitochondria -majority of chloroplast introns -several classes -require Mg2+ -no cofactor

  2. Domain Structure of a Group II Intron A 5’ exon 3’ exon

  3. Chemistry of Group II Self-Splicing 1st step 2nd step lariat

  4. Group II Self-Splicing Lariat Formation electron micrograph of Group II lariat Genes VII

  5. Group II X-ray Science 2008 320 77 - 82

  6. Group II Metal Sites

  7. “Homing” Endonucleases -some Group II introns contain ORF for DNA endonuclease activity and reverse transcriptase (RT)activity

  8. “When the junk isn’t junk” Nature (1996) 379, 402-3 -snoRNAs (small nucleolar) involved in RNA transcription -nucleoli are sites of rRNA transcription, processing , ribosomal subunit assembly -U22 snoRNA host gene (UHG) -exon sequences not conserved between species, introns conserved (a) (b)

  9. RNase P E. coli RNase P - the activity responsible for the maturation of the 5’ end of pre-tRNAs contains a protein component (C5) and an RNA component (M1)

  10. RNase P Model

  11. RNase P X-ray Proc Natl Acad Sci(2005) 102, 13392

  12. Protein Synthesis

  13. E. coli Ribosome -70S particle, MW ~2.5 x 106 -dissociable into small (30S) and large (50S) subunits -30S contains 16S RNA, 21 polypeptides -50S contains 5S, 23S RNA + 31 polypeptides “Although the ribosome has been crystallized…it is such a complex entity that it will be many years before its structure is known in molecular detail” - Voet and Voet, Biochemistry 1995

  14. Chemistry of Peptidyl Transfer B B + B

  15. Ribosome X-ray Structure Science (2000) 289:920-30

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