9T7L

Cryo-EM structure of the PseTnsAB paired-end complex (right end) in the presence of Mg

Summary for 9T7L

• Entry DOI: 10.2210/pdb9t7l/pdb
• EMDB information: 55638
• Descriptor: PseTnsAB artificial fusion protein, Transposon right-end, transferred strand, Transposon right-end, non-transferred strand, ... (4 entities in total)
• Functional Keywords: transposase, dna-binding, crispr-associated transposon, nuclease, dna binding protein
• Biological source: Pseudoalteromonas sp. S983; More
• Total number of polymer chains: 8
• Total formula weight: 447633.73

Authors

Finocchio, G.,Oberli, S.,Jinek, M. (deposition date: 2025-11-11, release date: 2026-06-03)

Primary citation

Walter, M.,Finocchio, G.,Oberli, S.,Hammerschmid, I.C.,Lampe, G.D.,Karan, J.,Swartjes, T.,Sternberg, S.H.,Jinek, M.,Querques, I.
Transposon end recognition and excision mechanisms of type I-F CRISPR-associated transposases.
Biorxiv, 2026

PubMed Abstract: CRISPR-associated transposons (CASTs) are Tn7-like elements that have co-opted RNA-guided CRISPR effectors for targeted DNA insertion. CASTs have been adapted as genome editing tools for programmable, site-specific integration. Among them, the type I-F system from e ( CAST) shows uniquely robust activity in human cells, yet its mechanistic basis remains poorly understood. Here, we present structural and biochemical analysis of the CAST transposase TnsAB. Biochemical reconstitution of transposon DNA excision defines key characteristics of the transposition mechanism. Cryogenic electron microscopy (cryo-EM) structures of TnsAB paired-end complexes reveal molecular determinants of transpososome assembly, transposon end recognition and cleavage. We validate these findings using biochemical and assays of structure-based transposase mutants, and provide mechanistic insights into the enhanced activity of a laboratory-evolved TnsAB variant. Together, our studies highlight molecular features underlying the efficiency of natural and engineered type I-F transposases and establish a mechanistic framework for their continued rational optimization.

PubMed: 42146515
DOI: 10.64898/2026.05.05.722991

Experimental method

ELECTRON MICROSCOPY (2.8 Å)