Inhibition of protein synthesis by spermine in growing cells of Staphylococcus aureus

Friedman, Mischa E. (Hebrew University, Jerusalem, Israel), and Uriel Bachrach. Inhibition of protein synthesis by spermine in growing cells of Staphylococcus aureus. J. Bacteriol. 92:49-55. 1966.-Staphylococcus aureus SFL 9725 incorporated valine-C(14) into cellular protein. This incorporation was inhibited by spermine when the pH of the culture was adjusted to 7.8, and the inhibition was antagonized partially by Mg(++). The incorporation of C(14)-labeled leucine, phenylalanine, lysine, arginine, and possibly glutamic acid was inhibited to a much greater extent than that of alanine, glycine, or threonine. The uptake of spermine-C(14) by S. aureus cells was rapid. More than 50% of the radioactivity resided in the soluble extract. The protein fraction of the soluble extract contained 99% of the recovered label, whereas the ribonucleic acid and deoxyribonucleic acid fractions contained little or no spermine-C(14).

Studies on the function of intracellular ribonucleases. V. Ribonuclease activity in ribosomes and polysomes prepared from rat liver and hepatomas

The RNase activity and properties of ribosome and polysome preparations from normal rat liver and some hepatomas have been examined. Polysome and ribosome preparations from the Novikoff, McCoy MDAB, and Dunning hepatomas had considerably higher specific RNase activity than corresponding preparations from normal rat liver, Novikoff ascites, or Morris 5123 hepatomas. The optimum pH of the RNase was approximately 8.5 for all samples tested, and the samples showed no evidence of latent RNase activity when treated with 3 M sodium chloride, EDTA, urea, or p-chloromercuribenzenesulfonic acid. The RNase activity appeared to be associated principally with breakdown products and/or subunits smaller than 80S. In the presence of Mg(++) ions, subunits could reaggregate to form monomer ribosomes indistinguishable from the natural products, but some of the reassociated ribosomes could contain RNase activity which had been bound to the smaller particles. Similar results were obtained with spermine. In the hepatomas, evidence was obtained for the preexistence of considerable amounts of the smaller, RNase-containing subunits in the cell. When a small amount of crystalline bovine pancreatic RNase was added to partly dissociated ribosomes, the RNase was found only in association with the smaller subunits, and little or no enzyme was taken up by ribosomes or polysomes. The results have led to the conclusion that RNase is not a normal constituent of the ribosome or polysome, but that RNase may become associated with these particulates if dissociation and reassociation take place. Some implications of these findings for the stability of messenger RNA and for the mechanism of its breakdown are discussed.

Reversal of the bactericidal reaction of serum by magnesium ion

Muschel, Louis H. (University of Minnesota, Minneapolis), and Jean E. Jackson. Reversal of the bactericidal reaction of serum by magnesium ion. J. Bacteriol. 91:1399-1402. 1966.-Magnesium ion was found to reverse the bactericidal action of the antibody-complement system. Concentrations of 0.03 to 0.11 m MgSO(4) or MgCl(2) were effective, provided that the reaction of the antibody-complement system did not proceed longer than 50 min. Salts of other monovalent and divalent cations, the polyamine, spermine, and several anticomplementary substances were inactive in reversing the serum bactericidal reaction. Thus, the bactericidal reaction of serum may be bacteriostatic under certain conditions, and this finding is compatible with the persistence of infection in certain diseases despite high levels of antibody.