1wq5
|
Crystal structure of tryptophan synthase alpha-subunit from Escherichia coli
OverviewOverview
When the tryptophan synthase alpha- and beta(2)-subunits combine to form, the alpha(2)beta(2)-complex, the enzymatic activity of each subunit is, stimulated by 1-2 orders of magnitude. To elucidate the structural basis, of this mutual activation, it is necessary to determine the structures of, the alpha- and beta-subunits alone and together with the, alpha(2)beta(2)-complex. The crystal structures of the tryptophan synthase, alpha(2)beta(2)-complex from Salmonella typhimurium, (Stalpha(2)beta(2)-complex) have already been reported. However, the, structures of the subunit alone from mesophiles have not yet been, determined. The structure of the tryptophan synthase alpha-subunit alone, from Escherichia coli (Ecalpha-subunit) was determined by an X-ray, crystallographic analysis at 2.3 A, which is the first report on the, subunits alone from the mesophiles. The biggest difference between the, structures of the Ecalpha-subunit alone and the alpha-subunit in the, Stalpha(2)beta(2)-complex (Stalpha-subunit) was as follows. Helix 2' in, the Stalpha-subunit, including an active site residue (Asp60), was changed, to a flexible loop in the Ecalpha-subunit alone. The conversion of the, helix to a loop resulted in the collapse of the correct active site, conformation. This region is also an important part for the mutual, activation in the Stalpha(2)beta(2)-complex and interaction with the, beta-subunit. These results suggest that the formation of helix 2'that is, essential for the stimulation of the enzymatic activity of the, alpha-subunit is constructed by the induced-fit mode involved in, conformational changes upon interaction between the alpha- and, beta-subunits. This also confirms the prediction of the conformational, changes based on the thermodynamic analysis for the association between, the alpha- and beta-subunits.
About this StructureAbout this Structure
1WQ5 is a Single protein structure of sequence from Escherichia coli with SO4 and GOL as ligands. Active as Tryptophan synthase, with EC number 4.2.1.20 Full crystallographic information is available from OCA.
ReferenceReference
Conformational changes in the alpha-subunit coupled to binding of the beta 2-subunit of tryptophan synthase from Escherichia coli: crystal structure of the tryptophan synthase alpha-subunit alone., Nishio K, Morimoto Y, Ishizuka M, Ogasahara K, Tsukihara T, Yutani K, Biochemistry. 2005 Feb 1;44(4):1184-92. PMID:15667212
Page seeded by OCA on Wed Nov 21 05:36:04 2007