1LBM

CRYSTAL STRUCTURE OF PHOSPHORIBOSYL ANTHRANILATE ISOMERASE (PRAI) IN COMPLEX WITH REDUCED 1-(O-CARBOXYPHENYLAMINO)-1-DEOXYRIBULOSE 5-PHOSPHATE (RCDRP)

Summary for 1LBM

• Entry DOI: 10.2210/pdb1lbm/pdb
• Descriptor: PHOSPHORIBOSYL ANTHRANILATE ISOMERASE, 1-(O-CARBOXY-PHENYLAMINO)-1-DEOXY-D-RIBULOSE-5-PHOSPHATE (3 entities in total)
• Functional Keywords: beta barrel, ligand complex, product analogue complex, tryptophan biosynthesis, isomerase
• Biological source: Thermotoga maritima
• Total number of polymer chains: 1
• Total formula weight: 23421.79

Authors

Hennig, M.,Sterner, R.,Kirschner, K. (deposition date: 2002-04-04, release date: 2002-12-18, Last modification date: 2023-08-16)

Primary citation

Henn-Sax, M.,Thoma, R.,Schmidt, S.,Hennig, M.,Kirschner, K.,Sterner, R.
Two (betaalpha)(8)-barrel enzymes of histidine and tryptophan biosynthesis have similar reaction mechanisms and common strategies for protecting their labile substrates
Biochemistry, 41:12032-12042, 2002

PubMed Abstract: The enzymes N'-[(5'-phosphoribosyl)formimino]-5-aminoimidazole-4-carboxamide ribonucleotide isomerase (HisA) and phosphoribosylanthranilate isomerase (TrpF) are sugar isomerases that are involved in histidine and tryptophan biosynthesis, respectively. Both enzymes have the (betaalpha)(8)-barrel fold and catalyze Amadori rearrangements of a thermolabile aminoaldose into the corresponding aminoketose. To identify those amino acids that are essential for catalysis, conserved residues at the active sites of both HisA and TrpF from the hyperthermophile Thermotoga maritima were replaced by site-directed mutagenesis, and the purified variants were investigated by steady-state enzyme kinetics. Aspartate 8, aspartate 127, and threonine 164 appeared to be important for the HisA reaction, whereas cysteine 7 and aspartate 126 appeared to be important for the TrpF reaction. On the basis of these results and the X-ray structure of a complex between TrpF and a bound product analogue, a reaction mechanism involving general acid-base catalysis and a Schiff base intermediate is proposed for both enzymes. A comparison of the HisA and TrpF enzymes from T. maritima and Escherichia coli showed that, at the physiological temperatures of 80 and 37 degrees C, respectively, the enzymes from the hyperthermophile have significantly higher catalytic efficiencies than the corresponding enzymes from mesophiles. These results suggest that HisA and TrpF have similar chemical reaction mechanisms and use the same strategy to prevent the loss of their thermolabile substrates.

PubMed: 12356303
DOI: 10.1021/bi026092h

Experimental method

X-RAY DIFFRACTION (2.8 Å)