US EPA

1168090 

Journal Article 

Chloromethane : tetrahydrofolate methyl transfer by two proteins from Methylobacterium chloromethanicum strain CM4 

Studer, A; Stupperich, E; Vuilleumier, S; Leisinger, T 

2001 

Yes 

European Journal of Biochemistry
ISSN: 0014-2956
EISSN: 1432-1033 

Wiley-Blackwell, 111 River Street Hoboken NJ 07030-5774 United States 

268 

10 

2931-2938 

English 

11358510 

WOS:000168968300022 

The cmuA and cmuB genes are required for growth of Methylobacterium chloromethanicum strain CM4 with chloromethane as the sole carbon source. While CmuB was previously shown to possess methylcobalamin:tetrahydrofolate methyltransferase activity, sequence analysis indicated that CmuA represented a novel and so far unique two-domain methyltransferase/corrinoid-binding protein involved in methyl transfer from chloromethane to a corrin moiety. CmuA was purified from wild-type M. chloromethanicum strain CM4 and characterized as a monomeric, cobalt-containing and zinc-containing enzyme of molecular mass 67 kDa with a bound vitamin B12 cofactor. In combination, CmuA and CmuB proteins catalyze the in vitro transfer of the methyl group of chloromethane to tetrahydrofolate, thus affording a direct link between chloromethane dehalogenation and core C1 metabolism of Methylobacterium. Chloromethane dehalogenase activity in vitro is limited by CmuB, as formation of methyltetrahydrofolate from chloromethane displays apparent Michaelis-Menten kinetics with respect to methylated CmuA, with an apparent Km of 0.27 microM and a Vmax of 0.45 U x mg(-1). This contrasts with sequence-related systems for methyl transfer from methanogens, which involve methyltransferase and corrinoid protein components in well-defined stoichiometric ratios. 

chloromethane; dehalogenation; Methylobacterium; methyltransferase; vitamin B12