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Crystal structure of lignin peroxidase
S L Edwards1, R Raag, H Wariishi
1Center for Advanced Research in Biotechnology, Rockville, MD 20850, USA.
Summary
The crystal structure of lignin peroxidase (LiP) from Phanerochaete chrysosporium reveals significant structural similarity to cytochrome c peroxidase, despite only 20% sequence identity. Key differences in heme-proximal residues explain distinct radical formation mechanisms during peroxide reactions.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Lignin peroxidase (LiP) is a crucial enzyme in lignin degradation.
- Understanding LiP's structure is key to its catalytic mechanism.
- High-resolution structural data for LiP was previously limited.
Purpose of the Study:
- To determine the high-resolution crystal structure of lignin peroxidase (LiP).
- To compare the structure of LiP with other related peroxidases.
- To elucidate structural basis for LiP's unique catalytic properties.
Main Methods:
- X-ray crystallography at 2.6 A resolution.
- Multiple isomorphous replacement methods.
- Simulated annealing refinement.
Main Results:
- The three-dimensional structure of LiP (343 residues) was determined, showing four disulfide bonds.
- LiP shares a similar helical fold and heme environment with cytochrome c peroxidase.
- Distinct differences include phenylalanine residues in LiP versus tryptophan in cytochrome c peroxidase near the heme.
Conclusions:
- LiP maintains a conserved peroxidase fold despite low sequence identity to cytochrome c peroxidase.
- Structural variations, particularly the presence of phenylalanines, explain LiP's distinct porphyrin pi cation radical formation.
- This structural insight aids in understanding lignin degradation pathways and enzyme engineering.