Transport of coenzyme M (2-mercaptoethanesulfonic acid) and methylcoenzyme M [(2-methylthio)ethanesulfonic acid] in Methanococcus voltae: identification of specific and general uptake systems.
A transport system for coenzyme M (2-mercaptoethanesulfonic acid [HS-CoM]) and methylcoenzyme M [(2-(methylthio)ethanesulfonic acid (CH3-S-CoM)] in Methanococcus voltae required energy, showed saturation kinetics, and concentrated both forms of coenzyme M against a concentration gradient. Transport required hydrogen and carbon dioxide for maximal uptake. CH3-S-CoM uptake was inhibited by N-ethylmaleimide and monensin. Both HS-CoM and CH3-S-CoM uptake showed sodium dependence. In wild-type M. voltae, HS-CoM uptake was concentration dependent, with a Vmax of 960 pmol/min per mg of protein and an apparent Km of 61 microM. Uptake of CH3-S-CoM showed a Vmax of 88 pmol/min per mg of protein and a Km of 53 microM. A mutant of M. voltae resistant to the coenzyme M analog 2-bromoethanesulfonic acid (BES) showed no uptake of CH3-S-CoM but accumulated HS-CoM at the wild-type rate. While the higher-affinity uptake system was specific for HS-CoM, the lower-affinity system mediated uptake of HS-CoM, CH3-S-CoM, and BES. Analysis of the intracellular coenzyme M pools in metabolizing cells showed an intracellular HS-CoM concentration of 14.8 mM and CH3-S-CoM concentration of 0.21 mM.
Dybas
M
M
Department of Microbiology, University of Illinois, Urbana 61801.
Konisky
J
J
D000693:Anaerobiosis; D001692:Biological Transport; D019605:Euryarchaeota / Q000378:metabolism*; D007700:Kinetics; D008623:Mercaptoethanol; D015080:Mesna / Q000138:chemical synthesis / Q000378:metabolism* / Q000031:analogs & derivatives; D011865:Radioisotope Dilution Technique; D013462:Sulfur Radioisotopes; D014316:Tritium
D013462:Sulfur Radioisotopes; D014316:Tritium; C023349:methyl coenzyme M; D008623:Mercaptoethanol; D015080:Mesna