Cryo-EM Structures and Regulation of Arabinofuranosyltransferase AftD from Mycobacteria

Abstract

<jats:title>SUMMARY</jats:title><jats:p><jats:italic>Mycobacterium tuberculosis</jats:italic> causes tuberculosis, a disease that kills over one million people each year. Its cell envelope is a common antibiotic target and has a unique structure due, in part, to two lipidated polysaccharides – arabinogalactan and lipoarabinomannan. Arabinofuranosyltransferase D (AftD) is an essential enzyme involved in assembling these glycolipids. We present the 2.9 Å resolution structure of <jats:italic>M. abscessus</jats:italic> AftD determined by single particle cryo-electron microscopy. AftD has a conserved GT-C glycosyltransferase fold and three carbohydrate binding modules. Glycan array analysis shows that AftD binds complex arabinose glycans. Additionally, AftD is non-covalently complexed with an acyl carrier protein (ACP). 3.4 and 3.5 Å structures of a mutant with impaired ACP binding reveal a conformational change that suggests the ACP may regulate AftD function. Using a conditional knock-out constructed in <jats:italic>M. smegmatis</jats:italic>, mutagenesis experiments confirm the essentiality of the putative active site and the ACP binding for AftD function.</jats:p>