More insights into the dynamic assembly and rotation of the archaellum motor machinery

Dimeric ArlJ forms a complex with ArlI, and conserved ArlJ residues—including the critical R341 at the ArlI interface—are required for interaction in archaellum rotation.

• Why it matters: The field lacks a clear mechanism for how ATP hydrolysis by ArlI is converted into rotation of the membrane platform ArlJ.
• What they did: Using single-molecule TIRF microscopy, conservation analysis, AlphaFold3 predictions, and co-purifications, the study mapped ArlJ residues needed for ArlI binding and tested them in motility assays in Haloferax volcanii.
• The result: The combined data support a torque-generating model where dimeric ArlJ engages ArlI through conserved residues, linking the interaction interface to rotational output.

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