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| {{STRUCTURE_1wq5| PDB=1wq5 | SCENE= }} | | {{STRUCTURE_1wq5| PDB=1wq5 | SCENE= }} |
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| '''Crystal structure of tryptophan synthase alpha-subunit from Escherichia coli'''
| | ===Crystal structure of tryptophan synthase alpha-subunit from Escherichia coli=== |
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| ==Overview==
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| 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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_15667212}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 15667212 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_15667212}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Tryptophan]] | | [[Category: Tryptophan]] |
| [[Category: Tryptophan synthase]] | | [[Category: Tryptophan synthase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 14:00:08 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 14:51:33 2008'' |
