Methanogens membrane function

Concerning the general topic of ferredoxin and redox proteins, it is important to note the existence of several of these in various methanogens. Ferredoxin has been reported in M barkeri [iQ2], M. thermophila [249,303], and Methanococcus thermolithotrophicus [304,305]. In one case, ferredoxin is required in electron transfer from carbon monoxide dehydrogenase to a membrane-bound hydrogenase in M. thermophila [306]. Another redox protein, referred to as a glutaredoxin-like protein , has been isolated from M. thermoautotrophicum [307], but has no known function. As mentioned above, MVH gene clusters contain a sequence for a polyferredoxin of unknown function. 

It would be of interest to test these hypotheses by examining the methanogens and thermophiles for the presence of FAS and acyl transferases and studying the effect of salt concentration, low pH and high temperature on their activities and on those of the mevalonate enzyme system. It may be noted that preliminary studies with M. thermo-autotrophicum have revealed the presence of a functional FAS producing fatty acids for acylation only of membrane proteins (Pugh and Kates, unpublished data). 

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