ABSTRACT
The Me transferases generally consist of readily dissociated subunits (or mod ules) for the separate binding of donor, acceptor, and corrinoid. They often possess a further “ activating” module for regenerating the Co(I) or Me-Co corrinoid after adventitious oxidation to the inactive Co(II) state, using ATP or AdoMet, respectively, to drive the reaction. Their structural organization further exemplifies the strategy (see Sec. 2.3) of using well-defined and interchangeable domains, with the corrinoid presumably held on the lower (a) side by the corrinoid binding domain, leaving the upper ((3) side free to interact in turn with domains involved with the substrates and activators.
