# NorQD AAA+ complex drives metal insertion by a twisting mechanism

## TL;DR

The paper explains how the NorQD complex helps insert metal ions into a protein by twisting and stretching it.

## Contribution

The study reveals a twisting mechanism by which the NorQD complex facilitates metal insertion into its target protein.

## Key findings

- NorQ and NorD interact through two key structural interfaces.
- NorQ activity remodels a linker region in NorD crucial for metal insertion.
- The NorQ complex applies a twisting and stretching force to enable metal insertion into NOR.

## Abstract

ATPases associated with diverse cellular activities (AAA+ -ATPases) catalyse a wide range of remodelling events in all phyla. AAA+ -ATPases of the MoxR-like family typically co-operate with von Willebrand factor type A (VWA) domain containing proteins to facilitate target remodelling and metal ion insertion, but their mechanism of action is poorly understood. We studied the bacterial AAA+ -ATPase NorQ in complex with its VWA domain partner protein NorD, which are essential for nitric oxide reductase (NOR) activity. Our cryo-EM structures and biochemical analyses show that NorQ and NorD engage through two key interfaces: (i) a finger-like extension protruding from the VWA domain that penetrates the central pore of the NorQ hexamer, and (ii) the NorD C- terminus, which contacts the post-sensor 1 loop of NorQ. Our data reveal that NorQ activity remodels a linker region in NorD essential for metal insertion. Together, these findings support a model in which the NorQ complex exerts a twisting and stretching force on the NorD linker, thereby enabling metal insertion into its target NOR.

AAA+ -ATPases drive diverse molecular remodeling processes in cells. Here, the authors characterize the interaction between the NorQ ATPase and its VWA domain partner NorD, and propose a twisting mechanism by which this chaperone complex remodels its target, cNOR, to enable iron insertion.