Crystal structure of precorrin-8x methyl mutase.
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Shipman LW, Li D, Roessner CA, Scott AI, Sacchettini JC
Crystal structure of precorrin-8x methyl mutase.
Structure. 2001 Jul 3;9(7):587-96.
- PubMed ID
- 11470433 [ View in PubMed]
- Abstract
BACKGROUND: The crystal structure of precorrin-8x methyl mutase (CobH), an enzyme of the aerobic pathway to vitamin B12, provides evidence that the mechanism for methyl migration can plausibly be regarded as an allowed [1,5]-sigmatropic shift of a methyl group from C-11 to C-12 at the C ring of precorrin-8x to afford hydrogenobyrinic acid. RESULTS: The dimeric structure of CobH creates a set of shared active sites that readily discriminate between different tautomers of precorrin-8x and select a discrete tautomer for sigmatropic rearrangement. The active site contains a strictly conserved histidine residue close to the site of methyl migration in ring C of the substrate. CONCLUSION: Analysis of the structure with bound product suggests that the [1,5]-sigmatropic shift proceeds by protonation of the ring C nitrogen, leading to subsequent methyl migration.