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| {{STRUCTURE_1qgn| PDB=1qgn | SCENE= }} | | {{STRUCTURE_1qgn| PDB=1qgn | SCENE= }} |
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| '''CYSTATHIONINE GAMMA-SYNTHASE FROM NICOTIANA TABACUM'''
| | ===CYSTATHIONINE GAMMA-SYNTHASE FROM NICOTIANA TABACUM=== |
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| ==Overview==
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| Cystathionine gamma-synthase catalyses the committed step of de novo methionine biosynthesis in micro-organisms and plants, making the enzyme an attractive target for the design of new antibiotics and herbicides. The crystal structure of cystathionine gamma-synthase from Nicotiana tabacum has been solved by Patterson search techniques using the structure of Escherichia coli cystathionine gamma-synthase. The model was refined at 2.9 A resolution to a crystallographic R -factor of 20.1 % (Rfree25.0 %). The physiological substrates of the enzyme, L-homoserine phosphate and L-cysteine, were modelled into the unliganded structure. These complexes support the proposed ping-pong mechanism for catalysis and illustrate the dissimilar substrate specificities of bacterial and plant cystathionine gamma-synthases on a molecular level. The main difference arises from the binding modes of the distal substrate groups (O -acetyl/succinyl versusO -phosphate). Central in fixing the distal phosphate of the plant CGS substrate is an exposed lysine residue that is strictly conserved in plant cystathionine gamma-synthases whereas bacterial enzymes carry a glycine residue at this position. General insight regarding the reaction specificity of transsulphuration enzymes is gained by the comparison to cystathionine beta-lyase from E. coli, indicating the mechanistic importance of a second substrate binding site for L-cysteine which leads to different chemical reaction types.
| | The line below this paragraph, {{ABSTRACT_PUBMED_10438597}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 10438597 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_10438597}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Methionine biosynthesis]] | | [[Category: Methionine biosynthesis]] |
| [[Category: Pyridoxal 5'-phosphate]] | | [[Category: Pyridoxal 5'-phosphate]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 06:14:51 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 05:01:25 2008'' |
