N5-methyl-tetrahydromethanopterin:coenzyme M methyltransferase of Methanosarcina strain Gö1 is an Na(+)-translocating membrane protein.
To determine the cellular localization of components of the methyltransferase system, we separated cell extracts of Methanosarcina strain Gö1 into cytoplasmic and inverted-vesicle fractions. Measurements demonstrated that 83% of the methylene-tetrahydromethanopterin reductase activity resided in the cytoplasm whereas 88% of the methyl-tetrahydromethanopterin:coenzyme M methyltransferase (methyltransferase) was associated with the vesicles. The activity of the methyltransferase was stimulated 4.6-fold by ATP and 10-fold by ATP plus a reducing agent [e.g., Ti(III)]. In addition, methyltransferase activity depended on the presence of Na+ (apparent Km = 0.7 mM) and Na+ was pumped into the lumen of the vesicles in the course of methyl transfer from methyl-tetrahydromethanopterin not only to coenzyme M but also to hydroxycobalamin. Both methyl transfer reactions were inhibited by 1-iodopropane and reconstituted by illumination. A model for the methyl transfer reactions is presented.
Becher
B
B
Institut für Mikrobiologie, Georg-August-Universität, Göttingen, Germany.
Müller
V
V
Gottschalk
G
G
D002352:Carrier Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D005557:Formaldehyde / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D015080:Mesna / Q000031:analogs & derivatives / Q000378:metabolism; D017020:Methanosarcina / Q000201:enzymology* / Q000378:metabolism*; D008780:Methyltransferases / Q000378:metabolism*; D008954:Models, Biological; D010084:Oxidation-Reduction; D012964:Sodium / Q000378:metabolism*
D002352:Carrier Proteins; D008565:Membrane Proteins; D005557:Formaldehyde; C023349:methyl coenzyme M; D006859:Hydrogen; D012964:Sodium; D008780:Methyltransferases; D015080:Mesna