Crystal Structure of the Escherichia Coli Tas Protein, an NADP(H)-Dependent Aldo-Keto Reductase

Published

November 1, 2003

Author(s)

G Obmolova, A Teplyakov, P P. Khil, A J. Howard, R D. Camerini-Otero, G L. Gilliland

Abstract

The tas gene of Escherichia coli encodes the uncharacterized protein of 38.5 kDa molecular weight. The amino acid sequence shows homology to the family of aldo-keto reductases that reduce aldehyde or ketone functional groups to primary or secondary alcohols. The basic chemical reaction is the stereospecific transfer of hydride between the nicotinamide ring of NADPH^a and a carbon center on the substrate molecule. The aldo-keto reductases metabolize a wide range of small molecule substrates including sugars, aliphatic aldephatic aldehydes, aromatic hydrocarbons, steroids, and prostaglandins.¹ For many members of the family, however, the physiological substrates are not known.Crystallographic studies of human aldose reductase^2-4 have established the molecular architecture, geometry of cofactor binding, and the catalytic mechanism of aldo-keto reductases. All members of the family have a (Β/α)₈ TIM barrel fold. The catalytic site with the bound NADP(H) cofactor is located at the C-terminal edge of the Β-strands. Loops surrounding the active site form the substrate recognition cylindrical surface. Crystal complexes with various inhibitors^5-8 have indicated the ability of aldo-keto reductases to accommodate a wide range of substrates due to the conformational flexibility of the recognition loops.Tas was identified as the gene able to complement the tyrosine requirement in E. coli auxotroph strains under starvation conditions,⁹ hece the name tas (tyrosine auxotropy suppressor). It is, however, not clear whether the enzymatic activity of the Tas protein directly substitutes for the lacking prephenate dehydrogenase activity of the auxotroph strain, or it is somehow involved in the mutation process resulting in slow-growing Tyr⁺ revertants.The crystal structure determination of Tas was undertaken as part of a structural genomics effort¹⁰ (http://s2f.carb.nits.gov) in order to assist with the functional assignment of the protein. The Tas protein from E. coli was cloned, expressed, and the crystal structure determined at 1.6- resolution.

Citation

Proteins-Structure Function And Genetics

Volume

53

Issue

2

Pub Type

Journals

Keywords

Beta/alpha-barrel, crystal structure, escherichia coli, NADP(H) aido-keto reductase, structural genomics

Citation

Obmolova, G. , Teplyakov, A. , Khil, P. , Howard, A. , Camerini-Otero, R. and Gilliland, G. (2003), Crystal Structure of the Escherichia Coli Tas Protein, an NADP(H)-Dependent Aldo-Keto Reductase, Proteins-Structure Function And Genetics (Accessed December 8, 2024)