2tsy
From Proteopedia
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CRYSTAL STRUCTURES OF MUTANT (BETAK87T) TRYPTOPHAN SYNTHASE ALPHA2 BETA2 COMPLEX WITH LIGANDS BOUND TO THE ACTIVE SITES OF THE ALPHA AND BETA SUBUNITS REVEAL LIGAND-INDUCED CONFORMATIONAL CHANGES
Overview
Three-dimensional structures are reported for a mutant (betaK87T), tryptophan synthase alpha2beta2 complex with either the substrate L-serine, (betaK87T-Ser) or product L-tryptophan (betaK87T-Trp) at the active site, of the beta-subunit, in which both amino acids form external aldimines, with the coenzyme, pyridoxal phosphate. We also present structures with, L-serine bound to the beta site and either alpha-glycerol 3-phosphate, (betaK87T-Ser-GP) or indole-3-propanol phosphate (betaK87T-Ser-IPP) bound, to the active site of the alpha-subunit. The results further identify the, substrate and product binding sites in each subunit and provide insight, into conformational changes that occur upon formation of these complexes., The two structures having ligands at the active sites of both alpha- and, beta-subunits reveal an important new feature, the ordering of, alpha-subunit loop 6 (residues 179-187). Closure of loop 6 isolates the, active site of the alpha-subunit from solvent and results in interaction, between alphaThr183 and the catalytic residue alphaAsp60. Other, conformational differences between the wild type and these two mutant, structures include a rigid-body rotation of the alpha-subunit of, approximately 5 degrees relative to the beta-subunit and large movements, of part of the beta-subunit (residues 93-189) toward the rest of the, beta-subunit. Much smaller differences are observed in the betaK87T-Ser, structure. Remarkably, binding of tryptophan to the beta active site, results in conformational changes very similar to those observed in the, betaK87T-Ser-GP and betaK87T-Ser-IPP structures, with exception of the, disordered alpha-subunit loop 6. These large-scale changes, the closure of, loop 6, and the movements of a small number of side chains in the, alpha-beta interaction site provide a structural base for interpreting the, allosteric properties of tryptophan synthase.
About this Structure
2TSY is a Protein complex structure of sequences from Salmonella typhimurium with NA, G3P and PLS as ligands. Active as Tryptophan synthase, with EC number 4.2.1.20 Structure known Active Sites: S1 and S2. Full crystallographic information is available from OCA.
Reference
Crystal structures of a mutant (betaK87T) tryptophan synthase alpha2beta2 complex with ligands bound to the active sites of the alpha- and beta-subunits reveal ligand-induced conformational changes., Rhee S, Parris KD, Hyde CC, Ahmed SA, Miles EW, Davies DR, Biochemistry. 1997 Jun 24;36(25):7664-80. PMID:9201907
Page seeded by OCA on Mon Nov 5 18:37:53 2007
