macrolide transmembrane transporter complex MacAB-TolC complex macrolide transporter MacAB-TolC complex 2013-09-23T11:29:28Z GO:1990196 bhm cellular_component The MacAB-TolC complex is a macrolide transporter complex found in E.coli and related gram-negative bacteria. Its transport activity is specific to macrolide compounds containing 14- and 15-membered lactones. It consists of the dimeric inner membrane ATPase MacB, the hexameric, periplasmic membrane fusion protein MacA and the trimeric outer membrane factor TolC.