title: Crystal structure of the essential Mycobacterium tuberculosis phosphopantetheinyl transferase PptT, solved as a fusion protein with maltose binding protein.
abstract: Phosphopantetheinyl transferases (PPTases) are key enzymes in the assembly-line production of complex molecules such as fatty acids, polyketides and polypeptides, where they activate acyl or peptidyl carrier proteins, transferring a 4'-phosphopantetheinyl moiety from coenzyme A (CoA) to a reactive serine residue on the carrier protein. The human pathogen Mycobacterium tuberculosis encodes two PPTases, both essential and therefore attractive drug targets. We report the structure of the type-II PPTase PptT, obtained from crystals of a fusion protein with maltose binding protein. The structure, at 1.75Å resolution (R=0.156, Rfree=0.191), reveals an α/β fold broadly similar to other type-II PPTases, but with differences in peripheral structural elements. A bound CoA is clearly defined with its pantetheinyl arm tucked into a hydrophobic pocket. Interactions involving the CoA diphosphate, bound Mg(2+) and three active site acidic side chains suggest a plausible pathway for proton transfer during catalysis.
authors.affiliation: Maurice Wilkins Centre and School of Biological Sciences, University of Auckland, Auckland, New Zealand.
authors.forename: James
authors.initials: J
authors.lastname: Jung
authors.affiliation: Maurice Wilkins Centre and School of Biological Sciences, University of Auckland, Auckland, New Zealand.
authors.forename: Ghader
authors.initials: G
authors.lastname: Bashiri
authors.affiliation: Maurice Wilkins Centre and School of Biological Sciences, University of Auckland, Auckland, New Zealand.
authors.forename: Jodie M
authors.initials: JM
authors.lastname: Johnston
authors.affiliation: School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand.
authors.forename: Alistair S
authors.initials: AS
authors.lastname: Brown
authors.affiliation: School of Biological Sciences, Victoria University of Wellington, Wellington, New Zealand.
authors.forename: David F
authors.initials: DF
authors.lastname: Ackerley
authors.affiliation: Maurice Wilkins Centre and School of Biological Sciences, University of Auckland, Auckland, New Zealand. Electronic address: ted.baker@auckland.ac.nz.
authors.forename: Edward N
authors.initials: EN
authors.lastname: Baker
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D018360:Crystallography, X-Ray; D058619:Maltose-Binding Proteins / Q000378:metabolism*; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017855:Transferases (Other Substituted Phosphate Groups) / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D058619:Maltose-Binding Proteins; C082662:phosphopantetheinyl transferase; D017855:Transferases (Other Substituted Phosphate Groups)
keywords: Acyl carrier protein; Crystal structure; MBP fusion protein; Mycobacterium tuberculosis; Phosphopantetheinyl transferase type-II