4atj

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spinqualitylabelsall models 4atj, resolution 2.50Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

DISTAL HEME POCKET MUTANT (H42E) OF RECOMBINANT HORSERADISH PEROXIDASE IN COMPLEX WITH BENZHYDROXAMIC ACID

Overview

The crystal structures of horseradish peroxidase C (HRPC) active-site, mutants H42E and R38S/H42E co-crystallized with benzhydroxamic acid (BHA), and ferulic acid (FA), respectively, have been solved. The 2.5 A crystal, structure of the H42E-BHA complex reveals that the side-chain O atoms of, Glu42 occupy positions that are very similar to the positions of the two, side-chain N atoms of the distal histidine in the wild-type HRPC-BHA, structure. The mutation disturbs the hydrogen-bonding network extending, from residue 42 to the distal calcium ion and results in the absence of, the water molecule that is usually ligated to this ion in plant, peroxidases. Consequently, the distal calcium ion is six- rather than, seven-coordinated. In the 2.0 A R38S/H42E structure the position of Glu42, is different and no FA is observed in the distal haem pocket. This is a, consequence of the absence of the Arg38 side chain, which limits the, flexibility of the Glu42 side chain and modulates its acidity, making it, unsuitable as a general acid-base catalyst in the reaction cycle. The, water ligated to the distal calcium ion is present, showing that the, wild-type distal hydrogen-bonding network is preserved. These results show, why a glutamic acid residue can substitute for the conserved distal, histidine in HRPC and that Arg38 plays a significant role in controlling, the positioning and ionization state of the residue at position 42., Furthermore, these structures indicate that changes in the distal cavity, are conveyed through the distal hydrogen-bonding network to the distal, calcium site.

About this Structure

4ATJ is a Single protein structure of sequence from Armoracia rusticana with CA, HEM and BHO as ligands. Active as Peroxidase, with EC number 1.11.1.7 Full crystallographic information is available from OCA.

Reference

Structural analysis of the two horseradish peroxidase catalytic residue variants H42E and R38S/H42E: implications for the catalytic cycle., Meno K, Jennings S, Smith AT, Henriksen A, Gajhede M, Acta Crystallogr D Biol Crystallogr. 2002 Oct;58(Pt 10 Pt 2):1803-12. Epub, 2002 Sep 28. PMID:12351824

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