1EQB

X-RAY CRYSTAL STRUCTURE AT 2.7 ANGSTROMS RESOLUTION OF TERNARY COMPLEX BETWEEN THE Y65F MUTANT OF E-COLI SERINE HYDROXYMETHYLTRANSFERASE, GLYCINE AND 5-FORMYL TETRAHYDROFOLATE

Summary for 1EQB

• Entry DOI: 10.2210/pdb1eqb/pdb
• Related: 1DFO
• Descriptor: SERINE HYDROXYMETHYLTRANSFERASE, GLYCINE, PYRIDOXAL-5'-PHOSPHATE, ... (5 entities in total)
• Functional Keywords: functional mutant, hydroxymethyltransferase, aat-like fold, one carbon metabolism, transferase
• Biological source: Escherichia coli
• Total number of polymer chains: 4
• Total formula weight: 184608.50

Authors

Contestabile, R.,Angelaccio, S.,Bossa, F.,Wright, H.T.,Scarsdale, N.,Kazanina, G.,Schirch, V. (deposition date: 2000-04-03, release date: 2000-04-19, Last modification date: 2024-02-07)

Primary citation

Contestabile, R.,Angelaccio, S.,Bossa, F.,Wright, H.T.,Scarsdale, N.,Kazanina, G.,Schirch, V.
Role of tyrosine 65 in the mechanism of serine hydroxymethyltransferase.
Biochemistry, 39:7492-7500, 2000

PubMed Abstract: Crystal structures of human and rabbit cytosolic serine hydroxymethyltransferase have shown that Tyr65 is likely to be a key residue in the mechanism of the enzyme. In the ternary complex of Escherichia coli serine hydroxymethyltransferase with glycine and 5-formyltetrahydrofolate, the hydroxyl of Tyr65 is one of four enzyme side chains within hydrogen-bonding distance of the carboxylate group of the substrate glycine. To probe the role of Tyr65 it was changed by site-directed mutagenesis to Phe65. The three-dimensional structure of the Y65F site mutant was determined and shown to be isomorphous with the wild-type enzyme except for the missing Tyr hydroxyl group. The kinetic properties of this mutant enzyme in catalyzing reactions with serine, glycine, allothreonine, D- and L-alanine, and 5,10-methenyltetrahydrofolate substrates were determined. The properties of the enzyme with D- and L-alanine, glycine in the absence of tetrahydrofolate, and 5, 10-methenyltetrahydrofolate were not significantly changed. However, catalytic activity was greatly decreased for serine and allothreonine cleavage and for the solvent alpha-proton exchange of glycine in the presence of tetrahydrofolate. The decreased catalytic activity for these reactions could be explained by a greater than 2 orders of magnitude increase in affinity of Y65F mutant serine hydroxymethyltransferase for these amino acids bound as the external aldimine. These data are consistent with a role for the Tyr65 hydroxyl group in the conversion of a closed active site to an open structure.

PubMed: 10858298
DOI: 10.1021/bi000032z

Experimental method

X-RAY DIFFRACTION (2.7 Å)