1995 Fiscal Year Final Research Report Summary
Study on the reaction mechanism of peroxidase based on its tertiary structure
| Project/Area Number |
06680654
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Biophysics
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| Research Institution | Osaka University |
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Principal Investigator |
FUKUYAMA Keiichi Osaka University, Department of Biology Professor, 理学部, 教授 (80032283)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Peroxidase / X-ray crystallographic analysis / Three-dimensional structure of protein / Coordination structure of heme iron |
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| Research Abstract |
1. Sequences of genomic DNA and cDNA coding for Arthromyces ramosus peroxidase (ARP) have been determined. The mature ARP consists of 344 amino acids with N-terminal pyroglutamic acid preceded by a signal peptide of 20 amino acid residues.
2. High resolution structures of cyanide- and triiodide-bound forms of ARP have shown that on ligand binding the conformation of the distal histidine changed markedly but that of distal arginine changed little. The heme iron in the cyanide complex (low-spin ferric) is located on the heme plane, whereas the iron in the triiodide complex (high-spin ferric) is displaced from the plane about 0.2A toward the proximal side.
3. Spectroscopic and crystallographic studies have shown that under physiological conditions the heme iron of ARP is in the pentacoordinated high-spin state and that at high pH the heme iron is able to bind ammonia forming the low-spin state. Comparison of the geometries around the water molecules at the distal side of the heme in peroxidases has suggested that the location of the water molecule is dominated by the orientation of the imidazole ring of the distal histidine rather than by interaction with the heme iron.
4. Two proposed calcium sites have been confirmed by X-ray anomalous scattering technique.
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