title: X-ray study of the conformational changes in the molecule of phosphopantetheine adenylyltransferase from Mycobacterium tuberculosis during the catalyzed reaction.
abstract: Structures of recombinant phosphopantetheine adenylyltransferase (PPAT) from Mycobacterium tuberculosis (PPATMt) in the apo form and in complex with the substrate ATP were determined at 1.62 and 1.70 Å resolution, respectively, using crystals grown in microgravity by the counter-diffusion method. The ATP molecule of the PPATMt-ATP complex was located with full occupancy in the active-site cavity. Comparison of the solved structures with previously determined structures of PPATMt complexed with the reaction product dephosphocoenzyme A (dPCoA) and the feedback inhibitor coenzyme A (CoA) was performed using superposition on C(α) atoms. The peculiarities of the arrangement of the ligands in the active-site cavity of PPATMt are described. The conformational states of the PPAT molecule in the consequent steps of the catalyzed reaction in the apo enzyme and the enzyme-substrate and enzyme-product complexes are characterized. It is shown that the binding of ATP and dPCoA induces the rearrangement of a short part of the polypeptide chain restricting the active-site cavity in the subunits of the hexameric enzyme molecule. The changes in the quaternary structure caused by this rearrangement are accompanied by a variation of the size of the inner water-filled channel which crosses the PPAT molecule along the threefold axis of the hexamer. The molecular mechanism of the observed changes is described.
authors.affiliation: Laboratory of X-ray Analysis Methods and Synchrotron Radiation, Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninsky Prospect 59, Moscow, Russian Federation. tostars@mail.ru
authors.forename: Vladimir
authors.initials: V
authors.lastname: Timofeev
authors.forename: Evgenia
authors.initials: E
authors.lastname: Smirnova
authors.forename: Larisa
authors.initials: L
authors.lastname: Chupova
authors.forename: Roman
authors.initials: R
authors.lastname: Esipov
authors.forename: Inna
authors.initials: I
authors.lastname: Kuranova
mesh_terms: D001483:Base Sequence; D055162:Biocatalysis; D018360:Crystallography, X-Ray; D017931:DNA Primers; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D009713:Nucleotidyltransferases / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011487:Protein Conformation
chemical_list: D017931:DNA Primers; D009713:Nucleotidyltransferases; C022315:pantetheine-phosphate adenylyltransferase