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Crystal structure of precorrin-8x methyl mutase
L W Shipman1, D Li, C A Roessner
1Department of Chemistry, Texas A&M University, College Station, TX 77843, USA. sacchett@tamu.edu
Structure (London, England : 1993)
|July 27, 2001
Summary
Precorrin-8x methyl mutase (CobH) crystal structure reveals a [1,5]-sigmatropic shift mechanism for vitamin B12 synthesis. This enzyme facilitates methyl group migration via a conserved histidine residue within its active site.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Investigates the aerobic pathway for vitamin B12 biosynthesis.
- Focuses on the enzyme precorrin-8x methyl mutase (CobH).
- Examines the mechanism of methyl migration in precorrin-8x.
Purpose of the Study:
- To elucidate the structural basis of the [1,5]-sigmatropic methyl shift catalyzed by CobH.
- To understand how CobH selects a specific tautomer of precorrin-8x for catalysis.
- To identify key residues involved in the methyl migration process.
Main Methods:
- X-ray crystallography of precorrin-8x methyl mutase (CobH).
- Structural analysis of the enzyme-substrate/product complex.
- Bioinformatic analysis to identify conserved residues.
Main Results:
- The dimeric structure of CobH forms shared active sites that discriminate tautomers.
- A conserved histidine residue is located near the methyl migration site in ring C.
- The crystal structure provides evidence for a [1,5]-sigmatropic shift of a methyl group.
Conclusions:
- The [1,5]-sigmatropic shift mechanism is supported by the CobH crystal structure.
- Protonation of the ring C nitrogen precedes methyl migration.
- CobH facilitates the conversion of precorrin-8x to hydrogenobyrinic acid.