Evidence that KpsT, the ATP-binding component of an ATP-binding cassette transporter, is exposed to the periplasm and associates with polymer during translocation of the polysialic acid capsule of Escherichia coli K1.

KpsT utilizes ATP to effect translocation of the polysialic acid capsule of Escherichia coli K1. We have previously proposed a mechanistic model for the action of this protein. Here, we provide evidence to support two predictions of the model: that KpsT associates with polymer and that KpsT is accessible from the periplasmic surface of the inner membrane.