|2j9x, resolution 1.90Å ()|
|Ligands:||, , ,|
|Related:||1a50, 1a5a, 1a5b, 1a5s, 1beu, 1bks, 1c29, 1c8v, 1c9d, 1cw2, 1cx9, 1fuy, 1k3u, 1k7e, 1k7f, 1k7x, 1k8x, 1k8y, 1k8z, 1kfb, 1kfc, 1kfe, 1kfj, 1kfk, 1qop, 1qoq, 1tjp, 1ttp, 1ubs, 1wbj, 2cle, 2clf, 2cli, 2clk, 2cll, 2clm, 2clo, 2trs, 2tsy, 2tys, 2wsy, 2j9y, 2j9z|
TRYPTOPHAN SYNTHASE IN COMPLEX WITH GP, ALPHA-D,L-GLYCEROL-PHOSPHATE, CS, PH6.5 - ALPHA AMINOACRYLATE FORM - (GP)E(A-A)
In the tryptophan synthase bienzyme complex, indole produced by substrate cleavage at the alpha-site is channeled to the beta-site via a 25 A long tunnel. Within the beta-site, indole and l-Ser react with pyridoxal 5'-phosphate in a two-stage reaction to give l-Trp. In stage I, l-Ser forms an external aldimine, E(Aex1), which converts to the alpha-aminoacrylate aldimine, E(A-A). Formation of E(A-A) at the beta-site activates the alpha-site >30-fold. In stage II, indole reacts with E(A-A) to give l-Trp. The binding of alpha-site ligands (ASLs) exerts strong allosteric effects on the reaction of substrates at the beta-site: the distribution of intermediates formed in stage I is shifted in favor of E(A-A), and the binding of ASLs triggers a conformational change in the beta-site to a state with an increased affinity for l-Ser. Here, we compare the behavior of new ASLs as allosteric effectors of stage I with the behavior of the natural product, d-glyceraldehyde 3-phosphate. Rapid kinetics and kinetic isotope effects show these ASLs bind with affinities ranging from micro- to millimolar, and the rate-determining step for conversion of E(Aex1) to E(A-A) is increased by 8-10-fold. To derive a structure-based mechanism for stage I, X-ray structures of both the E(Aex1) and E(A-A) states complexed with the different ASLs were determined and compared with structures of the ASL complexes with the internal aldimine [Ngo, H., Harris, R., Kimmich, N., Casino, P., Niks, D., Blumenstein, L., Barends, T. R., Kulik, V., Weyand, M., Schlichting, I., and Dunn, M. F. (2007) Biochemistry 46, 7713-7727].
Allosteric regulation of substrate channeling in tryptophan synthase: modulation of the L-serine reaction in stage I of the beta-reaction by alpha-site ligands., Ngo H, Kimmich N, Harris R, Niks D, Blumenstein L, Kulik V, Barends TR, Schlichting I, Dunn MF, Biochemistry. 2007 Jul 3;46(26):7740-53. Epub 2007 Jun 9. PMID:17559232
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
About this Structure
2j9x is a 2 chain structure with sequence from Salmonella enterica subsp. enterica serovar typhimurium. Full crystallographic information is available from OCA.
- Ngo H, Kimmich N, Harris R, Niks D, Blumenstein L, Kulik V, Barends TR, Schlichting I, Dunn MF. Allosteric regulation of substrate channeling in tryptophan synthase: modulation of the L-serine reaction in stage I of the beta-reaction by alpha-site ligands. Biochemistry. 2007 Jul 3;46(26):7740-53. Epub 2007 Jun 9. PMID:17559232 doi:10.1021/bi7003872