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Methylcobalamin:coenzyme M methyltransferase isoenzymes MtaA and MtbA from Methanosarcina barkeri

MPS-Authors

Harms,  Ulrike
Department of Biochemistry, Alumni, Max Planck Institute for Terrestrial Microbiology, Max Planck Society;
Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps- Universität, Marburg;

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Thauer,  Rudolf K.       
Department of Biochemistry, Alumni, Max Planck Institute for Terrestrial Microbiology, Max Planck Society;
Laboratorium für Mikrobiologie, Fachbereich Biologie, Philipps- Universität, Marburg;

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Citation

Harms, U., & Thauer, R. K. (1996). Methylcobalamin:coenzyme M methyltransferase isoenzymes MtaA and MtbA from Methanosarcina barkeri. European Journal of Biochemistry, 235(3), 653-659. doi:10.1111/j.1432-1033.1996.00653.x.


Cite as: https://hdl.handle.net/21.11116/0000-000F-95C1-E
Abstract
Methanosarcina barkeri is known to contain two methyltransferase isoenzymes, here designated MtaA and MtbA, which catalyze the formation of methyl-coenzyme M from methylcobalamin and coenzyme M. The genes encoding the two soluble 34-kDa proteins have been cloned and sequenced. mtaA and mtbA were found to be located in different parts of the genome, each forming a monocystronic transcription unit. Northern blot analysis revealed that mtaA is preferentially transcribed when M. barkeri is grown on methanol and the mtbA gene when the organism is grown on H2/CO2 or trimethylamine. Comparison of the deduced amino acid sequences revealed the sequences of the two isoenzymes to be 37% identical. Both isoenzymes showed sequence similarity to uroporphyrinogen III decarboxylase from Escherichia coli. The mtaA gene was tagged with a sequence encoding six His placed six bp before the mtaA start codon, and was functionally overexpressed in E. coli. 25% of the E. coli protein was found to be active methyltransferase which could be, purified in two steps to apparent homogenity with a 70% yield.