Novel mannose carrier in the trypanosomatid Crithidia fasciculata behaving as a short alpha-saturated polyprenyl phosphate.

Crithidia fasciculata cells incubated with [14C]glucose or membranes derived from the same protozoan incubated with GDP-[14C]mannose were found to synthesize a lipid monophosphate mannose. No glucosylated mild acid-labile compound was formed in vivo or in vitro when UDP-[14C]glucose was used instead of GDP-[14C]mannose. The lipid moiety of the mannosyl derivative formed behaved as a polyprenol having 11 isoprene residues as judged by t.l.c. and be gel filtration in sodium deoxycholate-containing buffers. The mannolipid was not broken on treatment with hot phenol, suggesting the existence of an alpha-saturated isoprene unit. This is the first case reported in which a mannosyl phospholipid involved in sugar transfer in a eukaryotic cell behaves as if it was similar to that of bacterial polyprenols, although having its putative alpha-isoprene unit saturated to the same extent as dolichols from higher organisms.