1cs1
From Proteopedia
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CYSTATHIONINE GAMMA-SYNTHASE (CGS) FROM ESCHERICHIA COLI
Overview
The transsulfuration enzyme cystathionine gamma-synthase (CGS) catalyses, the pyridoxal 5'-phosphate (PLP)-dependent gamma-replacement of, O-succinyl-L-homoserine and L-cysteine, yielding L-cystathionine. The, crystal structure of the Escherichia coli enzyme has been solved by, molecular replacement with the known structure of cystathionine beta-lyase, (CBL), and refined at 1.5 A resolution to a crystallographic R-factor of, 20.0%. The enzyme crystallizes as an alpha4 tetramer with the subunits, related by non-crystallographic 222 symmetry. The spatial fold of the, subunits, with three functionally distinct domains and their quaternary, arrangement, is similar to that of CBL. Previously proposed reaction, mechanisms for CGS can be checked against the structural model, allowing, interpretation of the catalytic and substrate-binding functions of, individual active site residues. Enzyme-substrate models pinpoint specific, residues responsible for the substrate specificity, in agreement with, structural comparisons with CBL. Both steric and electrostatic designs of, the active site seem to achieve proper substrate selection and productive, orientation. Amino acid sequence and structural alignments of CGS and CBL, suggest that differences in the substrate-binding characteristics are, responsible for the different reaction chemistries. Because CGS catalyses, the only known PLP-dependent replacement reaction at Cgamma of certain, amino acids, the results will help in our understanding of the chemical, versatility of PLP.
About this Structure
1CS1 is a Single protein structure of sequence from Escherichia coli with DHD as ligand. Active as Transferred entry: 2.5.1.48, with EC number 4.2.99.9 Structure known Active Sites: PLA, PLB, PLC and PLD. Full crystallographic information is available from OCA.
Reference
Crystal structure of Escherichia coli cystathionine gamma-synthase at 1.5 A resolution., Clausen T, Huber R, Prade L, Wahl MC, Messerschmidt A, EMBO J. 1998 Dec 1;17(23):6827-38. PMID:9843488
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