title: Structure of mycobacterial maltokinase, the missing link in the essential GlgE-pathway.
abstract: A novel four-step pathway identified recently in mycobacteria channels trehalose to glycogen synthesis and is also likely involved in the biosynthesis of two other crucial polymers: intracellular methylglucose lipopolysaccharides and exposed capsular glucan. The structures of three of the intervening enzymes - GlgB, GlgE, and TreS - were recently reported, providing the first templates for rational drug design. Here we describe the structural characterization of the fourth enzyme of the pathway, mycobacterial maltokinase (Mak), uncovering a eukaryotic-like kinase (ELK) fold, similar to methylthioribose kinases and aminoglycoside phosphotransferases. The 1.15 Å structure of Mak in complex with a non-hydrolysable ATP analog reveals subtle structural rearrangements upon nucleotide binding in the cleft between the N- and the C-terminal lobes. Remarkably, this new family of ELKs has a novel N-terminal domain topologically resembling the cystatin family of protease inhibitors. By interfacing with and restraining the mobility of the phosphate-binding region of the N-terminal lobe, Mak's unusual N-terminal domain might regulate its phosphotransfer activity and represents the most likely anchoring point for TreS, the upstream enzyme in the pathway. By completing the gallery of atomic-detail models of an essential pathway, this structure opens new avenues for the rational design of alternative anti-tubercular compounds.
authors.affiliation: IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
authors.forename: Joana
authors.initials: J
authors.lastname: Fraga
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Maranha
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.
authors.forename: Vitor
authors.initials: V
authors.lastname: Mendes
authors.affiliation: IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
authors.forename: Pedro José Barbosa
authors.initials: PJ
authors.lastname: Pereira
authors.affiliation: CNC - Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal.
authors.forename: Nuno
authors.initials: N
authors.lastname: Empadinhas
authors.affiliation: IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
authors.forename: Sandra
authors.initials: S
authors.lastname: Macedo-Ribeiro
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry*; D005964:Glucosyltransferases / Q000737:chemistry / Q000235:genetics; D007700:Kinetics; D053858:Metabolic Networks and Pathways; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000235:genetics; D010802:Phylogeny; D017510:Protein Folding; D020836:Protein Structure, Quaternary
chemical_list: D000255:Adenosine Triphosphate; D005964:Glucosyltransferases; D017853:Phosphotransferases (Alcohol Group Acceptor); C100489:maltokinase