1a5b: Difference between revisions
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==Overview== | ==Overview== | ||
The reversible cleavage of indole-3-glycerol by the alpha-subunit of, tryptophan synthase has been proposed to be catalyzed by alphaGlu49 and, alphaAsp60. Although previous x-ray crystallographic structures of the, tryptophan synthase alpha2beta2 complex showed an interaction between the, carboxylate of alphaAsp60 and the bound inhibitor indole-3-propanol, phosphate, the carboxylate of alphaGlu49 was too distant to play its, proposed role. To clarify the structural and functional roles of, alphaGlu49, we have determined crystal structures of a mutant (alphaD60N), alpha2beta2 complex in the presence and absence of the true substrate, indole-3-glycerol phosphate. The enzyme in the crystal cleaves, indole-3-glycerol phosphate very slowly at room temperature but not under, cryo-conditions of ... | The reversible cleavage of indole-3-glycerol by the alpha-subunit of, tryptophan synthase has been proposed to be catalyzed by alphaGlu49 and, alphaAsp60. Although previous x-ray crystallographic structures of the, tryptophan synthase alpha2beta2 complex showed an interaction between the, carboxylate of alphaAsp60 and the bound inhibitor indole-3-propanol, phosphate, the carboxylate of alphaGlu49 was too distant to play its, proposed role. To clarify the structural and functional roles of, alphaGlu49, we have determined crystal structures of a mutant (alphaD60N), alpha2beta2 complex in the presence and absence of the true substrate, indole-3-glycerol phosphate. The enzyme in the crystal cleaves, indole-3-glycerol phosphate very slowly at room temperature but not under, cryo-conditions of 95 K. The structure of the complex with the true, substrate obtained by cryo-crystallography reveals that indole-3-glycerol, phosphate and indole-3-propanol phosphate have similar binding modes but, different torsion angles. Most importantly, the side chain of alphaGlu49, interacts with 3-hydroxyl group of indole-3-glycerol phosphate as, proposed. The movement of the side chain of alphaGlu49 into an extended, conformation upon binding the true substrate provides evidence for an, induced fit mechanism. Our results demonstrate how cryo-crystallography, and mutagenesis can provide insight into enzyme mechanism. | ||
==About this Structure== | ==About this Structure== | ||
1A5B is a | 1A5B is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Salmonella_typhimurium Salmonella typhimurium] with K, IGP and PLP as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Tryptophan_synthase Tryptophan synthase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=4.2.1.20 4.2.1.20] Structure known Active Sites: S1 and S2. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1A5B OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: true substrate indole-3-glycerol phosphate in the a-subunit]] | [[Category: true substrate indole-3-glycerol phosphate in the a-subunit]] | ||
''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 5 14:37:33 2007'' | ||