
==== Front
bioRxiv
BIORXIV
bioRxiv
2692-8205
Cold Spring Harbor Laboratory

10.1101/2024.09.05.611425
preprint
1
Article
Structural Basis for Dimerization and Activation of UvrD-family Helicases
Chadda Ankita http://orcid.org/0000-0003-0282-3249

Nguyen Binh
Lohman Timothy M.
Galburt Eric A. http://orcid.org/0000-0003-4314-3215

06 9 2024
2024.09.05.611425https://creativecommons.org/licenses/by-nc-nd/4.0/ This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which allows reusers to copy and distribute the material in any medium or format in unadapted form only, for noncommercial purposes only, and only so long as attribution is given to the creator.
http://biorxiv.org/lookup/doi/10.1101/2024.09.05.611425
nihpp-2024.09.05.611425.pdf
Abstract

UvrD-family helicases are superfamily 1A motor proteins that function during DNA replication, recombination, repair, and transcription. UvrD family monomers translocate along single stranded (ss) DNA but need to be activated by dimerization to unwind DNA in the absence of force or accessory factors. However, prior structural studies have only revealed monomeric complexes. Here, we report the first structures of a dimeric UvrD-family helicase, Mycobacterium tuberculosis UvrD1, both free and bound to a DNA junction. In each structure, the dimer interface occurs between the 2B subdomains of each subunit. The apo UvrD1 dimer is observed in symmetric compact and extended forms indicating substantial flexibility. This symmetry is broken in the DNA-bound dimer complex with leading and trailing subunits adopting distinct conformations. Biochemical experiments reveal that the E. coli UvrD dimer shares the same 2B-2B interface. In contrast to the dimeric structures, an inactive, auto-inhibited UvrD1 DNA-bound monomer structure reveals 2B subdomain-DNA contacts that are likely inhibitory. The major re-orientation of the 2B subdomains that occurs upon UvrD1 dimerization prevents these duplex DNA interactions, thus relieving the auto-inhibition. These structures reveal that the 2B subdomain serves a major regulatory role rather than participating directly in DNA unwinding.
==== Body
pmc
