1. Group II Self-Splicing Introns -pre-rRNA of fungal and plant mitochondria -majority of chloroplast introns -several classes -require Mg 2+ -no cofactor

2. 5’ exon3’ exon Domain Structure of a Group II Intron A

4. Chemistry of Group II Self-Splicing 1st step2nd step lariat

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

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

7. Group II Metal Sites

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

9. “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)

10. 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)

11. RNase P Model

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

13. Protein Synthesis

14. E. coli Ribosome -70S particle, MW ~2.5 x 10 6 -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

15. Chemistry of Peptidyl Transfer B B+B+ B

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