RexA is a family of bacterial anti-phage proteins. It forms one partner in the two-component abortive infection system, Abi, of E. coli in partnership with RexB, a membrane-anchored ion- channel. Two RexA are needed to activate one RexB, and activation causes opening of the channel, the efflux of cations, a drop in cellular levels of ATP and subsequent death of the host cell and abortion of the phage infecting process which requires ATP.

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