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J. Bacteriol., Aug 1995, 4410-4416, Vol 177, No. 15
SA Burke and JA Krzycki
An assay which allowed detection of proteins involved in the
trimethylamine- or monomethylamine (MMA)-dependent methylation of coenzyme
M (CoM) was developed. The two activities could be separated by
anion-exchange chromatography. The unresolved activity responsible for
MMA:CoM methyl transfer eluted from a gel permeation column in the
molecular mass range of 32 kDa. The activity was purified to two monomeric
proteins of 40 and 29 kDa. The preparation contained protein- bound
corrinoid in a mixture of Co(II) and Co(III) states, as well as
methyl-B12:CoM methyltransferase (MT2) activity. N-terminal sequence
analysis demonstrated that the polypeptides were two previously identified
proteins of undefined physiological function. The smaller polypeptide was
the monomeric 29-kDa corrinoid protein. The larger polypeptide was the "A"
isozyme of MT2. Individually purified preparations of both proteins
increased the rate of MMA-dependent CoM methylation by approximately 1.7
mumol/min/mg of purified protein above background activity in the extract
of methanol-grown cells. These results indicate that the 29-kDa corrinoid
protein and the "A" isozyme of MT2 function in methanogenesis from MMA. A
likely mechanism is that the 29-kDa corrinoid is methylated by MMA and the
methyl group is then transferred by the "A" isozyme of MT2 to CoM.
Copyright © 1995, American Society for Microbiology
Involvement of the "A" isozyme of methyltransferase II and the 29- kilodalton corrinoid protein in methanogenesis from monomethylamine
Department of Microbiology, Ohio State University, Columbus 43210, USA.
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