Kiwa is a membrane-embedded defence supercomplex activated at phage attachment sites (Cell)

Zhang and colleagues, including Franklin Nobrega, report in Cell that the widespread two-component Kiwa defence system, a transmembrane sensor KwaA and a DNA-binding effector KwaB, assembles into a large membrane-associated supercomplex (cryo-EM). On phage binding, KwaA senses infection at the membrane and KwaB binds the ejected phage DNA, inhibiting replication and late transcription without killing the host cell. The phage DNA-mimic protein Gam directly binds and inhibits KwaB, but co-expression with the Gam-targeted RecBCD system restores protection by Kiwa.