Bacterial multi-solute transporters.

Bacterial membrane proteins of the SbmA/BacA family are multi-solute transporters that mediate the uptake of structurally diverse hydrophilic molecules, including aminoglycoside antibiotics and antimicrobial peptides. Some family members are full-length ATP-binding cassette (ABC) transporters, whereas other members are truncated homologues that lack the nucleotide-binding domains and thus mediate ATP-independent transport. A recent cryo-EM structure of the ABC transporter Rv1819c from Mycobacterium tuberculosis has shed light on the structural basis for multi-solute transport and has provided insight into the mechanism of transport. Here, we discuss how the protein architecture makes SbmA/BacA family transporters prone to inadvertent import of antibiotics and speculate on the question which physiological processes may benefit from multi-solute transport.