title: Comparing Galactan Biosynthesis inMycobacterium tuberculosisandCorynebacterium diphtheriae.
abstract: The suborder Corynebacterineae encompasses species likeCorynebacterium glutamicum, which has been harnessed for industrial production of amino acids, as well asCorynebacterium diphtheriaeandMycobacterium tuberculosis, which cause devastating human diseases. A distinctive component of the Corynebacterineae cell envelope is the mycolyl-arabinogalactan (mAG) complex. The mAG is composed of lipid mycolic acids, and arabinofuranose (Araf) and galactofuranose (Galf) carbohydrate residues. Elucidating microbe-specific differences in mAG composition could advance biotechnological applications and lead to new antimicrobial targets. To this end, we compare and contrast galactan biosynthesis inC. diphtheriaeandM. tuberculosisIn each species, the galactan is constructed from uridine 5'-diphosphate-α-d-galactofuranose (UDP-Galf), which is generated by the enzyme UDP-galactopyranose mutase (UGM or Glf). UGM and the galactan are essential inM. tuberculosis,but their importance in Corynebacterium species was not known. We show that small molecule inhibitors of UGM impedeC. glutamicumgrowth, suggesting that the galactan is critical in corynebacteria. Previous cell wall analysis data suggest the galactan polymer is longer in mycobacterial species than corynebacterial species. To explore the source of galactan length variation, aC. diphtheriaeortholog of theM. tuberculosiscarbohydrate polymerase responsible for the bulk of galactan polymerization, GlfT2, was produced, and its catalytic activity was evaluated. TheC. diphtheriaeGlfT2 gave rise to shorter polysaccharides than those obtained with theM. tuberculosisGlfT2. These data suggest that GlfT2 alone can influence galactan length. Our results provide tools, both small molecule and genetic, for probing and perturbing the assembly of the Corynebacterineae cell envelope.
authors.affiliation: From the Department of Biochemistry and.
authors.forename: Darryl A
authors.initials: DA
authors.lastname: Wesener
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Levengood
authors.affiliation: From the Department of Biochemistry and kiessling@chem.wisc.edu.|Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706.
authors.forename: Laura L
authors.identifier: 0000-0001-6829-1500
authors.initials: LL
authors.lastname: Kiessling
mesh_terms: D003353:Corynebacterium diphtheriae / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D005685:Galactans / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000378:metabolism; D019751:Intramolecular Transferases / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009169:Mycobacterium tuberculosis / Q000201:enzymology / Q000378:metabolism*; D019081:O Antigens / Q000737:chemistry; D058105:Polymerization
chemical_list: D005685:Galactans; D019081:O Antigens; D019751:Intramolecular Transferases; C098051:UDP-galactopyranose mutase
keywords: cell wall; enzyme catalysis; galactofuranose; glycobiology; glycosyltransferase; mycobacteria