Structural insights into trehalose capture and translocation by mycobacterial LpqY-SugABC

The human pathogen, Mycobacterium tuberculosis (Mtb) relies heavily on trehalose for both survival and pathogenicity. The type I ATP-binding cassette (ABC) transporter LpqY-SugABC is the only trehalose import pathway in Mtb. Conformational dynamics of ABC transporters is an important feature to explain how they operate, but experimental structures are determined in a static environment. Therefore, a detailed transport mechanism cannot be elucidated because there is a lack of intermediate structures. Here, we used single particle cryo-electron microscopy (cryo-EM) to determine the structure of the Mycobacterium smegmatis (M. smegmatis) trehalose-specific importer LpqY-SugABC complex in five different conformations. These structures have been classified and reconstructed from a single cryo-EM dataset. This study allows a comprehensive understanding of the trehalose recycling mechanism in Mycobacteria and also demonstrates the potential of single-particle cryo-EM to explore the dynamic structures of other ABC transporters and molecular machines.