Just like lipoarabinomannan (map00571
), arabinogalactan (AG) is a major heteropolysaccharide found on the mycobacterium cell wall. AG consists of a linear galactan chain of galactofuranosyl (Galf) residues covalently connected to peptidoglycan (PG), with branches of three similar arabinan chains comprising arabinofuranosyl (Araf) residues. The non-reducing ends of arabinans are often covalently attached to the long fatty acids of mycolic acids. Thus, the covalently linked network of PG and mycolylated AG, termed the mycolyl-arabinogalactan-peptidoglycan (mAGP) complex, forms an exceptionally robust cell wall and provides a permeability barrier to antibiotics.