Journal
STRUCTURE
Volume 9, Issue 7, Pages 587-596Publisher
CELL PRESS
DOI: 10.1016/S0969-2126(01)00618-9
Keywords
precorrin-8x; vitamin B-12; sigmatropic rearrangement
Funding
- NIAID NIH HHS [AI 43268] Funding Source: Medline
- NIDDK NIH HHS [2R01DK32034-18] Funding Source: Medline
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Background:The crystal structure of precorrin-8x methyl mutase (CobH), an enzyme of the aerobic pathway to vitamin B-12, 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.
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