Holliday junction branch migration driven by AAA+ ATPase motors

• Published in: Current opinion in structural biology 2023-10, Vol.82, p.102650, Article 102650
• Main Authors: Wald, Jiri, Marlovits, Thomas C.
• Format: Article
• Language: English
• Subjects: AAA+ ATPase; DNA recombination; Holliday junction; RuvAB
• ISSN: 0959-440X; 1879-033X; 1879-033X
• DOI: 10.1016/j.sbi.2023.102650

Holliday junctions are key intermediate DNA structures during genetic recombination. One of the first Holliday junction-processing protein complexes to be discovered was the well conserved RuvAB branch migration complex present in bacteria that mediates an ATP-dependent movement of the Holliday junction (branch migration). Although the RuvAB complex served as a paradigm for the processing of the Holliday junction, due to technical limitations the detailed structure and underlying mechanism of the RuvAB branch migration complex has until now remained unclear. Recently, structures of a reconstituted RuvAB complex actively-processing a Holliday junction were resolved using time-resolved cryo-electron microscopy. These structures showed distinct conformational states at different stages of the migration process. These structures made it possible to propose an integrated model for RuvAB Holliday junction branch migration. Furthermore, they revealed unexpected insights into the highly coordinated and regulated mechanisms of the nucleotide cycle powering substrate translocation in the hexameric AAA+ RuvB ATPase. Here, we review these latest advances and describe areas for future research. •Structure of the full RuvAB complex actively-processing the Holliday junction revealed.•Transition-state intermediates of RuvB AAA+ resolve the complete nucleotide cycle.•Conformation landscape of the nucleotide cycle uncovers the mechanism of chemo-mechanical coupling.•Usage of slowly hydrolysable ATPγS in time-resolved cryo-EM studies.