PMID: 23151631

Authors:

Timofeev V, Smirnova E, Chupova L, Esipov R, Kuranova I

Title:

X-ray study of the conformational changes in the molecule of phosphopantetheine adenylyltransferase from Mycobacterium tuberculosis during the catalyzed reaction.

Journal:

Acta Crystallogr D Biol Crystallogr. 2012 Dec;68(Pt 12):1660-70. doi:, 10.1107/S0907444912040206. Epub 2012 Nov 9.

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 A 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(alpha) 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.