4S2C

Covalent complex of E. coli transaldolase TalB with fructose-6-phosphate

Summary for 4S2C

• Entry DOI: 10.2210/pdb4s2c/pdb
• Related: 1ONR 3CWN 4RZ5 4RZ6 4S2B
• Descriptor: Transaldolase B, FRUCTOSE -6-PHOSPHATE, 1,2-ETHANEDIOL, ... (4 entities in total)
• Functional Keywords: tim barrel, pentose phosphate pathway, schiff base fructose 6-phosphate, transferase
• Biological source: Escherichia coli K-12
• Cellular location: Cytoplasm : P0A870
• Total number of polymer chains: 2
• Total formula weight: 75501.46

Authors

Stellmacher, L.,Sandalova, T.,Schneider, G.,Sprenger, G.A.,Samland, A.K. (deposition date: 2015-01-20, release date: 2016-01-20, Last modification date: 2024-11-20)

Primary citation

Stellmacher, L.,Sandalova, T.,Schneider, S.,Schneider, G.,Sprenger, G.A.,Samland, A.K.
Novel mode of inhibition by D-tagatose 6-phosphate through a Heyns rearrangement in the active site of transaldolase B variants.
Acta Crystallogr D Struct Biol, 72:467-476, 2016

PubMed Abstract: Transaldolase B (TalB) and D-fructose-6-phosphate aldolase A (FSAA) from Escherichia coli are C-C bond-forming enzymes. Using kinetic inhibition studies and mass spectrometry, it is shown that enzyme variants of FSAA and TalB that exhibit D-fructose-6-phosphate aldolase activity are inhibited covalently and irreversibly by D-tagatose 6-phosphate (D-T6P), whereas no inhibition was observed for wild-type transaldolase B from E. coli. The crystal structure of the variant TalB(F178Y) with bound sugar phosphate was solved to a resolution of 1.46 Å and revealed a novel mode of covalent inhibition. The sugar is bound covalently via its C2 atom to the ℇ-NH2 group of the active-site residue Lys132. It is neither bound in the open-chain form nor as the closed-ring form of D-T6P, but has been converted to β-D-galactofuranose 6-phosphate (D-G6P), a five-membered ring structure. The furanose ring of the covalent adduct is formed via a Heyns rearrangement and subsequent hemiacetal formation. This reaction is facilitated by Tyr178, which is proposed to act as acid-base catalyst. The crystal structure of the inhibitor complex is compared with the structure of the Schiff-base intermediate of TalB(E96Q) formed with the substrate D-fructose 6-phosphate determined to a resolution of 2.20 Å. This comparison highlights the differences in stereochemistry at the C4 atom of the ligand as an essential determinant for the formation of the inhibitor adduct in the active site of the enzyme.

PubMed: 27050126
DOI: 10.1107/S2059798316001170

Experimental method

X-RAY DIFFRACTION (2.2 Å)