An ABC transporter Wzm–Wzt catalyzes translocation of lipid-linked galactan across the plasma membrane in mycobacteria

Significance The cell envelope of Mycobacterium tuberculosis serves as a primary protective barrier of the pathogen, which claims more than a million lives each year. Its basis, the unique mycobacterial cell wall core, is composed of covalently linked peptidoglycan, branched heteropolysaccharide arabinogalactan, and mycolic acids. Construction of this complex structure located on the bacterial surface requires an array of enzymes acting on both sides of the plasma membrane, as well as translocation of metabolic intermediates from the cytoplasm to the periplasmic space. In this work, we characterized an ATP-binding cassette (ABC) transporter involved in the export of galactan polymer produced by cytoplasmic enzymes across the plasma membrane, providing an important insight into the biogenesis of a structure critical for pathogen survival.