Functional implications of an intermeshing cogwheel-like interaction between TolC and MacA in the action of macrolide-specific efflux pump MacAB-TolC.

The inner membrane transporter MacB requires the outer membrane factor TolC and the periplasmic adaptor protein MacA to form a functional tripartite complex. In this study, we used a chimeric protein containing the tip region of the TolC α-barrel to investigate the role of the TolC α-barrel tip region with regard to its interaction with MacA.

Recombinant functional multidomain hemoglobin from the gastropod Biomphalaria glabrata.

The extracellular hemoglobin multimer of the planorbid snail Biomphalaria glabrata , intermediate host of the human parasite Schistosoma mansoni , is presumed to be a 1.44 MDa complex of six 240 kDa polypeptide subunits, arranged as three disulfide‐bridged dimers. The complete amino acid sequence of two subunit types (BgHb1 and BgHb2), and the partial sequence of a third type (BgHb3) are known.

Funnel-like hexameric assembly of the periplasmic adapter protein in the tripartite multidrug efflux pump in gram-negative bacteria.

The Escherichia coli AcrAB-TolC pump is the principal multidrug exporter that confers intrinsic drug tolerance to the bacteria. The inner membrane transporter AcrB requires the outer membrane factor TolC and the periplasmic adapter protein AcrA. However, it remains ambiguous how the three proteins are assembled. In this study, a hexameric model of the adapter protein was generated based on the propensity for trimerization of a dimeric unit, and this model was further validated by presenting its channel-forming property that determines the substrate specificity.