Structural and functional characterization of a maltose/maltodextrin ABC transporter comprising a single solute binding domain (MalE) fused to the transmembrane subunit MalF

Publication date: Available online 4 September 2018Source: Research in MicrobiologyAuthor(s): Anke Licht, Martin Bommer, Tobias Werther, Kristin Neumann, Carolin Hobe, Erwin SchneiderAbstractCanonical ATP-binding cassette import systems rely on extracellular substrate binding proteins (SBP) for function. In gram-negative bacteria, SBPs are usually freely diffusible in the periplasm and, where studied, exist in excess over their cognate transporters. However, in vitro studies with the maltose transporter of Escherichia coli (MalFGK2) have demonstrated that mechanistically one copy of its SBP (MalE) per transport complex is sufficient for activity. To address whether such a condition is physiologically relevant, we have characterized a homolog of the E. coli system from the gram-negative bacterium Bdellovibrio bacteriovorus which has a single copy of a maltose binding domain fused to the MalF subunit. Both transporters share substrate specificity for maltose and linear maltodextrins. Specific ATPase and transport activities of the B. bacteriovorus transporter were comparable to those of the E. coli system assayed at a 1:1 molar ratio of MalE to the transport complex. While MalEEc was able to additionally increase ATPase activity of MalFGK2Bb, the isolated MalE domain of B. bacteriovorus failed to stimulate the E. coli system. Strikingly, interactions of the MalE domain with the transmembrane subunits during the transport cycle as studied by site-specific cross-linking were foun...
Source: Research in Microbiology - Category: Microbiology Source Type: research