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| Title | Topological crossing in the misfolded ribozyme resolved by cryo-EM. |
|---|---|
| Journal, issue, pages | Proc Natl Acad Sci U S A, Vol. 119, Issue 37, Page e2209146119, Year 2022 |
| Publish date | Sep 13, 2022 |
 Authors | Shanshan Li / Michael Z Palo / Grigore Pintilie / Xiaojing Zhang / Zhaoming Su / Kalli Kappel / Wah Chiu / Kaiming Zhang / Rhiju Das /   |
| PubMed Abstract | The group I intron has been a key system in the understanding of RNA folding and misfolding. The molecule folds into a long-lived misfolded intermediate (M) , which has been known to form extensive ...The group I intron has been a key system in the understanding of RNA folding and misfolding. The molecule folds into a long-lived misfolded intermediate (M) , which has been known to form extensive native-like secondary and tertiary structures but is separated by an unknown kinetic barrier from the native state (N). Here, we used cryogenic electron microscopy (cryo-EM) to resolve misfolded structures of the L-21 ScaI ribozyme. Maps of three M substates (M1, M2, M3) and one N state were achieved from a single specimen with overall resolutions of 3.5 Å, 3.8 Å, 4.0 Å, and 3.0 Å, respectively. Comparisons of the structures reveal that all the M substates are highly similar to N, except for rotation of a core helix P7 that harbors the ribozyme's guanosine binding site and the crossing of the strands J7/3 and J8/7 that connect P7 to the other elements in the ribozyme core. This topological difference between the M substates and N state explains the failure of 5'-splice site substrate docking in M, supports a topological isomer model for the slow refolding of M to N due to a trapped strand crossing, and suggests pathways for M-to-N refolding. |
 External links | Proc Natl Acad Sci U S A / PubMed:36067294 / PubMed Central |
| Methods | EM (single particle) |
| Resolution | 3.01 - 4.01 Å |
| Structure data | EMDB-33425, PDB-7xsk: EMDB-33426, PDB-7xsl: EMDB-33427, PDB-7xsm: EMDB-33428, PDB-7xsn: |
| Source |
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 Keywords |  RNA / Misfolded Tetrahymena Ribozyme / Topological Crossing / Cryo-EM / refolding |
