3c20
From Proteopedia
OCA (Talk | contribs)
(New page: 200px <!-- The line below this paragraph, containing "STRUCTURE_3c20", creates the "Structure Box" on the page. You may change the PDB parameter (which sets the PD...)
Next diff →
Revision as of 10:35, 30 April 2008
Crystal Structure of Threonine-sensitive Aspartokinase from Methanococcus jannaschii with L-aspartate
Overview
The commitment step to the aspartate pathway of amino acid biosynthesis is the phosphorylation of aspartic acid catalyzed by aspartokinase (AK). Most microorganisms and plants have multiple forms of this enzyme, and many of these isofunctional enzymes are subject to feedback regulation by the end products of the pathway. However, the archeal species M. jannaschii has only a single, monofunctional form of AK. The substrate L-aspartate binds to this recombinant enzyme in two different orientations, providing the first structural evidence supporting the relaxed regiospecificity previously observed with several alternative substrates of E. coli AK (Angeles et al., Biochemistry 31, 799, 1992). Binding of the nucleotide substrate triggers significant domain movements that result in a more compact quaternary structure. In contrast, the highly cooperative binding of the allosteric regulator L-threonine to multiple sites on this dimer of dimers leads to a more open enzyme structure. A comparison of these structures supports a mechanism for allosteric regulation of AK in which the domain movements induced by threonine binding causes displacement of the substrates from the enzyme resulting in a relaxed, inactive conformation.
About this Structure
3C20 is a Single protein structure of sequence from Methanocaldococcus jannaschii. Full crystallographic information is available from OCA.
Reference
The structural basis for allosteric Inhibition of a threonine-sensitive aspartokinase., Liu X, Pavlovsky AG, Viola RE, J Biol Chem. 2008 Mar 11;. PMID:18334478 Page seeded by OCA on Wed Apr 30 13:35:16 2008
