Mycobacterium tuberculosis arabinosyltransferase complex (EmbABC) (EmbABC)

The Mycobacterium tuberculosis arabinosyltransferase complex, primarily composed of the EmbA, EmbB, and EmbC proteins, is an essential enzymatic system responsible for the assembly of the mycobacterial cell wall (Zhang et al., 2020, Science). These integral membrane glycosyltransferases catalyze the transfer of D-arabinofuranosyl residues from the donor molecule decaprenyl-phospho-arabinose (DPA) to the growing arabinan chains of arabinogalactan and lipoarabinomannan (Goude et al., 2009, Molecular Microbiology). Arabinogalactan is a major structural component that links the peptidoglycan layer to the outer mycolic acids, while lipoarabinomannan is a key lipoglycan involved in host-pathogen interactions and immune modulation (UniProt P9WNK3). Because these polysaccharides are essential for the structural integrity and survival of the bacterium, the complex is a validated therapeutic target. The first-line antitubercular drug ethambutol specifically inhibits these enzymes by acting as a substrate analog, leading to increased cell wall permeability and bacterial death (DrugBank DB00330). Resistance to ethambutol frequently arises through mutations in the embB gene, which encodes a core component of the complex, highlighting its clinical significance (Safi et al., 2013, Nature Communications). Understanding the structural biology of this complex is vital for developing next-generation inhibitors to combat multi-drug resistant tuberculosis.

Other names

EmbAEmbBEmbCArabinosyltransferase AArabinosyltransferase BArabinosyltransferase CEthambutol-sensitive arabinosyltransferaseEmbABC complex

Ethambutol acts as an antimetabolite that competes with the substrate decaprenyl-phospho-arabinose (DPA) for binding to the EmbA, EmbB, and EmbC enzymes, thereby inhibiting the polymerization of arabinose into the cell wall components arabinogalactan and lipoarabinomannan (Zhang et al., 2020, Science; PubChem CID 14052).