Bacterial signal peptide-independent protein export: HlyB-directed secretion of hemolysin.

Bacterial ABC transporter proteins are associated with a great number of cellular processes. While many of the best characterised examples are involved in the import of small molecules into the cell, others mediate export of substrates, especially hydrophilic proteins. This article focuses on these bacterial ABC exporters, in particular the HlyB protein which is central to secretion of the 110 kDa hemolysin across both the cytoplasmic and outer membranes. This is an example of non-conventional protein export which does not require an N-terminal signal sequence or the cellular SecA-dependent machinery.