Molecular insights into the mechanism of ATP-hydrolysis by the NBD of the ABC-transporter HlyB

Abstract 

The ABC-transporter HlyB is a central element of the Type I protein secretion machinery, dedicated to export the E. coli toxin HlyA in a single step across the two membranes of the cell envelope. Here, we discuss recent insights into the structure and the mechanism of ATP-hydrolysis by the NBD of HlyB. Combining structural and biochemical data, we have suggested that substrate-assisted catalysis (SAC), but not general base catalysis, is responsible for ATP-hydrolysis in this NBD and might also operate in other NBDs. Finally, the implications and advantages of SAC are discussed in the context of ATP-induced dimerization of the NBDs.

Abbreviations: ABC, ATP-binding cassette, Hly, haemolysin, NBD, nucleotide-binding domain, SAC, substrate-assisted catalysis, TMD, transmembrane domain

Keywords: ABC-transporters, Dimerization, Nucleotide-binding domain, Substrate-assisted catalysis, Crystal structures