title: Structure of Streptomyces maltosyltransferase GlgE, a homologue of a genetically validated anti-tuberculosis target.
abstract: GlgE is a recently identified (1→4)-α-d-glucan:phosphate α-d-maltosyltransferase involved in α-glucan biosynthesis in bacteria and is a genetically validated anti-tuberculosis drug target. It is a member of the GH13_3 CAZy subfamily for which no structures were previously known. We have solved the structure of GlgE isoform I from Streptomyces coelicolor and shown that this enzyme has the same catalytic and very similar kinetic properties to GlgE from Mycobacterium tuberculosis. The S. coelicolor enzyme forms a homodimer with each subunit comprising five domains, including a core catalytic α-amylase-type domain A with a (β/α)(8) fold. This domain is elaborated with domain B and two inserts that are specifically configured to define a well conserved donor pocket capable of binding maltose. Domain A, together with domain N from the neighboring subunit, forms a hydrophobic patch that is close to the maltose-binding site and capable of binding cyclodextrins. Cyclodextrins competitively inhibit the binding of maltooligosaccharides to the S. coelicolor enzyme, showing that the hydrophobic patch overlaps with the acceptor binding site. This patch is incompletely conserved in the M. tuberculosis enzyme such that cyclodextrins do not inhibit this enzyme, despite acceptor length specificity being conserved. The crystal structure reveals two further domains, C and S, the latter being a helix bundle not previously reported in GH13 members. The structure provides a framework for understanding how GlgE functions and will help guide the development of inhibitors with therapeutic potential.
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, United Kingdom.
authors.forename: Karl
authors.initials: K
authors.lastname: Syson
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, United Kingdom.
authors.forename: Clare E M
authors.initials: CEM
authors.lastname: Stevenson
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, United Kingdom.
authors.forename: Martin
authors.initials: M
authors.lastname: Rejzek
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, United Kingdom.
authors.forename: Shirley A
authors.initials: SA
authors.lastname: Fairhurst
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, United Kingdom.
authors.forename: Alap
authors.initials: A
authors.lastname: Nair
authors.affiliation: Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, United Kingdom.
authors.forename: Celia J
authors.initials: CJ
authors.lastname: Bruton
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, United Kingdom.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Field
authors.affiliation: Department of Molecular Microbiology, John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, United Kingdom.
authors.forename: Keith F
authors.initials: KF
authors.lastname: Chater
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, United Kingdom.
authors.forename: David M
authors.initials: DM
authors.lastname: Lawson
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, Norfolk NR4 7UH, United Kingdom. Electronic address: stephen.bornemann@jic.ac.uk.
authors.forename: Stephen
authors.initials: S
authors.lastname: Bornemann
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D001665:Binding Sites; D002384:Catalysis; D005964:Glucosyltransferases / Q000737:chemistry* / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000737:chemistry; D007700:Kinetics; D008320:Maltose / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D010766:Phosphorylation; D011487:Protein Conformation; D020033:Protein Isoforms; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013302:Streptomyces / Q000201:enzymology*
chemical_list: D000995:Antitubercular Agents; D020033:Protein Isoforms; D008320:Maltose; D005964:Glucosyltransferases; C436710:maltosyltransferase; D006026:Glycoside Hydrolases