Figure 1.

LtrA RNP with IEP consisting of different functional domains. (A) Structure of the group II intron-LrtA complex as established by cryo-EM. Six structural domains of the RNA (gray) are labeled I through VI. EBS1 and EBS2 point to the exon-binding sites within domain I of the intron RNA. The 5′ and 3′ ends of the intron RNA are marked, and the catalytic adenosine (A) at the branch point (BP) is highlighted green by space-filling. The bound fragment of mRNA captured in the cryo-EM study is magenta. Structural domains of LtrA are colored: NTE, light blue; RT fingers/palm domain, purple; thumb domain, dark blue; DNA-binding domain, green; and the endonuclease domain, cyan. (B) Comparison of domain organization of the 2 group II IEPs, LtrA and RIM, colored as in panel A. RIM is a truncated version of the full-length protein. Structures in this and subsequent figures were generated using Chimera ²³.