1WBJ

wildtype tryptophan synthase complexed with glycerol phosphate

Summary for 1WBJ

• Entry DOI: 10.2210/pdb1wbj/pdb
• 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 1TTQ 1UBS 2CLE 2CLF 2CLI 2CLK 2CLL 2CLM 2CLO 2TRS 2TSY 2TYS 2WSY
• Descriptor: TRYPTOPHAN SYNTHASE ALPHA CHAIN, TRYPTOPHAN SYNTHASE BETA CHAIN, SN-GLYCEROL-3-PHOSPHATE, ... (6 entities in total)
• Functional Keywords: lyase, pyridoxal phosphate, tryptophan biosynthesis
• Biological source: SALMONELLA TYPHIMURIUM; More
• Total number of polymer chains: 2
• Total formula weight: 71928.69

Authors

Kulik, V.,Weyand, M.,Schlichting, I. (deposition date: 2004-11-01, release date: 2006-05-24, Last modification date: 2025-04-09)

Primary citation

Kulik, V.,Hartmann, E.,Weyand, M.,Frey, M.,Gierl, A.,Niks, D.,Dunn, M.F.,Schlichting, I.
On the Structural Basis of the Catalytic Mechanism and the Regulation of the Alpha Subunit of Tryptophan Synthase from Salmonella Typhimurium and Bx1 from Maize, Two Evolutionarily Related Enzymes.
J.Mol.Biol., 352:608-, 2005

PubMed Abstract: Indole is a reaction intermediate in at least two biosynthetic pathways in maize seedlings. In the primary metabolism, the alpha-subunit (TSA) of the bifunctional tryptophan synthase (TRPS) catalyzes the cleavage of indole 3-glycerol phosphate (IGP) to indole and d-glyceraldehyde 3-phosphate (G3P). Subsequently, indole diffuses through the connecting tunnel to the beta-active site where it is condensed with serine to form tryptophan and water. The maize enzyme, BX1, a homolog of TSA, also cleaves IGP to G3P and indole, and the indole is further converted to 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one, a secondary plant metabolite. BX1 cleaves IGP significantly faster to G3P and indole than does TSA. In line with their different biological functions, these two evolutionary related enzymes differ significantly in their regulatory aspects while catalyzing the same chemistry. Here, the mechanism of IGP cleavage by TSA was analyzed using a novel transition state analogue generated in situ by reaction of 2-aminophenol and G3P. The crystal structure of the complex shows an sp3-hybridized atom corresponding to the C3 position of IGP. The catalytic alphaGlu49 rotates to interact with the sp3-hybridized atom and the 3' hydroxyl group suggesting that it serves both as proton donor and acceptor in the alpha-reaction. The second catalytic residue, alphaAsp60 interacts with the atom corresponding to the indolyl nitrogen, and the catalytically important loop alphaL6 is in the closed, high activity conformation. Comparison of the TSA and TSA-transition state analogue structures with the crystal structure of BX1 suggests that the faster catalytic rate of BX1 may be due to a stabilization of the active conformation: loop alphaL6 is closed and the catalytic glutamate is in the active conformation. The latter is caused by a substitution of the residues that stabilize the inactive conformation in TRPS.

PubMed: 16120446
DOI: 10.1016/J.JMB.2005.07.014

Experimental method

X-RAY DIFFRACTION (1.5 Å)