9K9J

Cryo-EM structure of linear intron of Anabaena tRNA(Leu) precursor

Summary for 9K9J

• Entry DOI: 10.2210/pdb9k9j/pdb
• EMDB information: 62191
• Descriptor: RNA (251-MER), MAGNESIUM ION (2 entities in total)
• Functional Keywords: anabaena trna(leu) precursor, self-folding, splicing, cyclization, cryo-em, rna
• Biological source: Anabaena
• Total number of polymer chains: 1
• Total formula weight: 81447.49

Authors

Zhang, X.,Li, S.,Zhang, K. (deposition date: 2024-10-26, release date: 2026-04-22, Last modification date: 2026-06-10)

Primary citation

Zhang, X.,An, L.,Yang, W.,Yi, R.,Liu, J.,Li, S.,Zhang, K.
Self-splicing and cyclization mechanisms of the full-length Anabaena pre-tRNA.
Nat.Chem.Biol., 22:948-959, 2026

PubMed Abstract: Group I introns are catalytic RNAs capable of self-splicing and generating circular RNAs, processes central to RNA metabolism and biotechnology. Yet, full-length ribozyme structures containing entire exon sequences and the structural basis of postsplicing circularization have remained limited. Using cryo-electron microscopy, we resolved multiple conformational states of the full-length Anabaena tRNA(Leu) precursor, capturing key intermediates of splicing and cyclization. In the apo state, the exons preassemble into a mature tRNA-like conformation that promotes P1 helix formation. Transitions through the splicing states involve substantial rearrangements essential for catalysis. Unlike other group I introns, the Anabaena intron circularizes without sequence loss, using its guanosine-binding site as the catalytic center. Mutational analyses confirm that G37 reorientation and a conserved wobble receptor motif precisely position the circularization site, driving efficient cyclization even in engineered PIE systems. These findings uncover unique mechanisms of RNA catalysis and establish structure-based optimization for advancing RNA circularization technologies.

PubMed: 41981295
DOI: 10.1038/s41589-026-02205-1

Experimental method

ELECTRON MICROSCOPY (3.46 Å)