1QGN

CYSTATHIONINE GAMMA-SYNTHASE FROM NICOTIANA TABACUM

Summary for 1QGN

• Entry DOI: 10.2210/pdb1qgn/pdb
• Descriptor: PROTEIN (CYSTATHIONINE GAMMA-SYNTHASE), PYRIDOXAL-5'-PHOSPHATE (3 entities in total)
• Functional Keywords: methionine biosynthesis, pyridoxal 5'-phosphate, gamma-family, lyase
• Biological source: Nicotiana tabacum (common tobacco)
• Total number of polymer chains: 8
• Total formula weight: 386520.92

Authors

Steegborn, C.,Messerschmidt, A.,Laber, B.,Streber, W.,Huber, R.,Clausen, T. (deposition date: 1999-05-02, release date: 1999-08-25, Last modification date: 2023-08-16)

Primary citation

Steegborn, C.,Messerschmidt, A.,Laber, B.,Streber, W.,Huber, R.,Clausen, T.
The crystal structure of cystathionine gamma-synthase from Nicotiana tabacum reveals its substrate and reaction specificity.
J.Mol.Biol., 290:983-996, 1999

PubMed Abstract: 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.

PubMed: 10438597
DOI: 10.1006/jmbi.1999.2935

Experimental method

X-RAY DIFFRACTION (2.9 Å)