Structural basis of directionality control in large serine integrases.

Structural analysis reveals that large serine integrases use conformational changes and RDF-mediated repositioning to control DNA recombination directionality, with distinct complexes for integration and excision.

• Why it matters: Understanding how integrases enforce unidirectional DNA insertion or excision is crucial for advancing genome editing technologies, yet structural mechanisms have been unclear.
• What they did: Researchers determined eight high-resolution structures of SPβ integrase-DNA complexes along both reaction pathways, capturing intermediates and product-bound states to elucidate conformational dynamics.
• The result: Findings show that integrase conformational shifts and RDF-induced repositioning of the coiled-coil subdomain determine active complex formation and lock conformations, enabling targeted engineering of genome editing tools.