Study of the cytoskeleton and lipid biosynthetic system of an archaeon Thermoplasma

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(1) Cytoskeleton-like structures of Thermoplasma were biochemically analyzed. Cells of Thermoplasma were treated by non-ionic detergent Triton X-100. The solubilized proteins were fractionated by the combination of anion-exchange-column chromatography and gel-exclusion chromatography. Several fractions of proteins that can reversibly polymerize were recovered. Tubular structures and net-like structures were found in some of those fractions by electron microscopic inspection. Peptide composition of the fractions was analyzed by SDS-polyacrylamide gel electophoresis.(2) Carbon 14-labeled mevalonic acid was used to trace the biosynthetic pathway of ether-membrane lipids in Thermoplasma. Polar ether-lipid fraction of Thermoplasma was extracted from the cells grown in the presence of C14-mevalonic acid. The extracted ether-lipids were analyzed by two-dimensional thin layer chromatography. Lipids were recovered from respective spot of TLC plates and the structures of the lipids were analyzed and estimated. After 2-h incubation, major polar tetraetherlipid, which has phosphatidylglycerol and a sugar molecule, was accumulated in the cells. In the presence of the inhibitor terbinafine, biosynthesis of the major polar lipid was inhibited and a diether lipid was accumulated. After the removal of the inhibitor, biosynthesis of polar lipids was analyzed by thin layer chromatography. The model of the biosynthetic pathway of the tetra-lipids was proposed.