SNAP output for PDB entry 8glx [SNAP web server]

PDB-id

8glx; SNAP-derived features in text and JSON formats; DNAproDB

Class

DNA binding protein-DNA

Method

cryo-EM (3.88 Å)

Summary

Cryoem structure of the tnsc(1-503)-tnsd(1-318)-DNA complex in a 6:2:1 stoichiometry from e. coli tn7

Reference

Shen Y, Krishnan SS, Petassi MT, Hancock MA, Peters JE, Guarne A (2024): "Assembly of the Tn7 targeting complex by a regulated stepwise process." Mol.Cell, 84, 2368-2381.e6. doi: 10.1016/j.molcel.2024.05.012.

Abstract

The Tn7 family of transposons is notable for its highly regulated integration mechanisms, including programmable RNA-guided transposition. The targeting pathways rely on dedicated target selection proteins from the TniQ family and the AAA+ adaptor TnsC to recruit and activate the transposase at specific target sites. Here, we report the cryoelectron microscopy (cryo-EM) structures of TnsC bound to the TniQ domain of TnsD from prototypical Tn7 and unveil key regulatory steps stemming from unique behaviors of ATP- versus ADP-bound TnsC. We show that TnsD recruits ADP-bound dimers of TnsC and acts as an exchange factor to release one protomer with exchange to ATP. This loading process explains how TnsC assembles a heptameric ring unidirectionally from the target site. This unique loading process results in functionally distinct TnsC protomers within the ring, providing a checkpoint for target immunity and explaining how insertions at programmed sites precisely occur in a specific orientation across Tn7 elements.