title: Synthesis of α-glucan in mycobacteria involves a hetero-octameric complex of trehalose synthase TreS and Maltokinase Pep2.
abstract: Recent evidence established that the cell envelope of Mycobacterium tuberculosis, the bacillus causing tuberculosis (TB), is coated by an α-glucan-containing capsule that has been implicated in persistence in a mouse infection model. As one of three known metabolic routes to α-glucan in mycobacteria, the cytoplasmic GlgE-pathway converts trehalose to α(1 → 4),α(1 → 6)-linked glucan in 4 steps. Whether individual reaction steps, catalyzed by trehalose synthase TreS, maltokinase Pep2, and glycosyltransferases GlgE and GlgB, occur independently or in a coordinated fashion is not known. Here, we report the crystal structure of M. tuberculosis TreS, and show by small-angle X-ray scattering and analytical ultracentrifugation that TreS forms tetramers in solution. Together with Pep2, TreS forms a hetero-octameric complex, and we demonstrate that complex formation markedly accelerates maltokinase activity of Pep2. Thus, complex formation may act as part of a regulatory mechanism of the GlgE pathway, which overall must avoid accumulation of toxic pathway intermediates, such as maltose-1-phosphate, and optimize the use of scarce nutrients.
authors.affiliation: School of Biosciences, University of Birmingham , Edgbaston, Birmingham B15 2TT, U.K.
authors.forename: Rana
authors.initials: R
authors.lastname: Roy
authors.forename: Veeraraghavan
authors.initials: V
authors.lastname: Usha
authors.forename: Ali
authors.initials: A
authors.lastname: Kermani
authors.forename: David J
authors.initials: DJ
authors.lastname: Scott
authors.forename: Eva I
authors.initials: EI
authors.lastname: Hyde
authors.forename: Gurdyal S
authors.initials: GS
authors.lastname: Besra
authors.forename: Luke J
authors.initials: LJ
authors.lastname: Alderwick
authors.forename: Klaus
authors.initials: K
authors.lastname: Fütterer
mesh_terms: D000818:Animals; D020134:Catalytic Domain; D056831:Coordination Complexes / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004305:Dose-Response Relationship, Drug; D005936:Glucans / Q000096:biosynthesis* / Q000378:metabolism; D005964:Glucosyltransferases / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D056831:Coordination Complexes; D005936:Glucans; D005964:Glucosyltransferases; C099692:trehalose synthase; D017853:Phosphotransferases (Alcohol Group Acceptor); C100489:maltokinase
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