Surprise! A hidden B12 cofactor catalyzes a radical methylationRadical S-adenosylmethionine (SAM) (RS) methylases perform methylation reactions at unactivated carbon and phosphorus atoms. RS enzymes typically abstract a hydrogen from their substrates, generating a substrate-centered radical; class B RS methylases catalyze methyl transfer from SAM to cobalamin and then to a substrate-centered carbon or phosphorus radical. Radle et al. now show that Mmp10, an RS enzyme implicated in the methylation of Arg-285 in methyl coenzyme M reductase, binds a methylcobalamin cofactor required for methyl transfer from SAM to a peptide substrate.
Balancing on the road less traveledSitting down to the task of writing, I found my pen drifting inexorably to a personal recollection of the metaphorical transcontinental road that I had traveled to become a scientist, instead of reviewing a facet of our scientific contributions. Factors that prepared me for my improbable journey in an era when international calls were operator-assisted and unaffordable and the internet was the stuff of science fiction were my family’s love and the sheltered environment of my all-girls school and college experiences, which nurtured my self-confidence.