Polyamines of sulfur-dependent archaebacteria and their role in protein synthesis.

Several strains of the sulfur-dependent archaebacterium, Sulfolobus, were analyzed for their polyamine content. Caldine (norspermidine), spermidine, and thermine were found to be major components in all of the cells tested. The most abundant polyamine in all cultures examined was spermidine. The Langworthy strain had the highest spermine content, whereas S. acidocaldarius strain no. 7 was devoid of this polyamine. Cultures of strain no. 7 grown at 70 degrees C were rich in spermidine and caldine (triamines) and the thermine: spermidine ratio was much lower than that of cultures grown at 78 degrees C. Equal amounts of thermine and spermidine were present in strain DSM 1616. Preincubation of Langworthy strain extracts at 10 degrees C did not overcome the requirement for polyamines in protein synthesis. Putrescine exerted a concentration-dependent inhibition of the spermine-induced stimulation of protein synthesis at 70 degrees C. Increasing concentrations (6 and 9 mM) of spermine and thermine progressively inhibited poly(U)-dependent phenylalanine incorporation at 45 degrees C to about the same extent, whereas the same concentrations of these polyamines had little effect on the reaction at 70 degrees C. Although 3 mM spermine had only a slight stimulatory effect on the attachment of phenylalanine to tRNA at 65 degrees C, this polyamine had a pronounced effect on the formation of 70S ribosomes in a standard buffer containing 10 mM Mg2+. Increasing the Mg2+ concentration to 30 mM in the absence of spermine was even more effective in causing the reassociation of subunits to form 70S particles.