Thermoplasma Cytoskeleton and Calmodulin

Electron micrographs have been obtained showing Thermoplasma acidophilum in amoeboid shapes attached to the surface of sulfur crystals. (2) Anti-actin antibodies reacted weakly with a 90 kDa protein in Western Blot analysis. Other cytoskeleton-related antibodies did not react. (3) Cytoplasmic extracts of T. acidophilum increased in viscosity upon incubation. Optimal conditions were approximately physiological. During incubation a subset of previously-soluble proteins became sedimentable by low speed centrifugation. (4) Extraction with nonionic detergents left an insoluble residue of several protein species. (5) A calcium-affected protein has been identified as ferredoxin. It binds Ca(++) with an affinity near 10 to the 6th power/M. (6) By autoradiography using phosphorus-32, hundreds of proteins are phosphorylated in vivo in T. acidophilum. Keywords: Archaebacteria, Superoxide dismutase, Algae.