2c2b
From Proteopedia
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CRYSTALLOGRAPHIC STRUCTURE OF ARABIDOPSIS THALIANA THREONINE SYNTHASE COMPLEXED WITH PYRIDOXAL PHOSPHATE AND S-ADENOSYLMETHIONINE
Overview
Threonine synthase (TS) is a fold-type II pyridoxal phosphate, (PLP)-dependent enzyme that catalyzes the ultimate step of threonine, synthesis in plants and microorganisms. Unlike the enzyme from, microorganisms, plant TS is activated by S-adenosylmethionine (AdoMet)., The mechanism of activation has remained unknown up to now. We report here, the crystallographic structures of Arabidopsis thaliana TS in complex with, PLP (aTS) and with PLP and AdoMet (aTS-AdoMet), which show with atomic, detail how AdoMet activates TS. The aTS structure reveals a PLP, orientation never previously observed for a type II PLP-dependent enzyme, and explains the low activity of plant TS in the absence of its allosteric, activator. The aTS-AdoMet structure shows that activation of the enzyme, upon AdoMet binding triggers a large reorganization of active site loops, in one monomer of the structural dimer and allows the displacement of PLP, to its active conformation. Comparison with other TS structures shows that, activation of the second monomer may be triggered by substrate binding., This structure also discloses a novel fold for two AdoMet binding sites, located at the dimer interface, each site containing two AdoMet effectors, bound in tandem. Moreover, aTS-AdoMet is the first structure of an enzyme, that uses AdoMet as an allosteric effector.
About this Structure
2C2B is a Single protein structure of sequence from Arabidopsis thaliana with SAM and TRS as ligands. Active as Threonine synthase, with EC number 4.2.3.1 Full crystallographic information is available from OCA.
Reference
Allosteric threonine synthase. Reorganization of the pyridoxal phosphate site upon asymmetric activation through S-adenosylmethionine binding to a novel site., Mas-Droux C, Biou V, Dumas R, J Biol Chem. 2006 Feb 24;281(8):5188-96. Epub 2005 Nov 29. PMID:16319072
Page seeded by OCA on Wed Nov 21 08:59:23 2007
