The enzyme, characterized from the bacterium Streptomyces laurentii, is involved in thiostrepton biosynthesis. It is a radical SAM enzyme that contains a [4Fe-4S] center and a methylcob(III)alamin cofactor. It has an exceptional reaction mechanism as the S-adenosyl-L-methionine (SAM) is not bound to the [4Fe-4S] center and does not produce a 5'-deoxyadenosyl radical but instead is believed to be involved in binding of the L-tryptophan substrate. After transfer of the methyl group from methylcob(III)alaminIn a methyl transfer from SAM to the generated cob(I)alamin takes place, preparing the enzyme for the next catalytic cycle. The original methyl group configuration is preserved.
Blaszczyk AJ, Silakov A, Zhang B, Maiocco SJ, Lanz ND, Kelly WL, Elliott SJ, Krebs C, Booker SJ
Title
Spectroscopic and Electrochemical Characterization of the Iron-Sulfur and Cobalamin Cofactors of TsrM, an Unusual Radical S-Adenosylmethionine Methylase.
