A mutation livS (livS1 in KA231) that occurred in a Salmonella typhimurium LT2 mutant strain CE5 (ilvC8 brnQ4) expressed pleiotropic effects on cellular characteristics. The mutation not only resulted in derepression of the transport of branched-chain amino acids (Ohnishi et al. 1980 ), but also altered the properties of the ribosome. Ribosomes of KA2313 (brnQ4 livS1), an Ilv+ transductant of KA231 from the wild-type donor, appeared to be more unstable than those of the ancestral strain KA204

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... rnQ4) in a Tris-HC1 buffer without MgC12. When ribosomes of KA2313 were suspended in the buffer, they released substantial amounts of smaller proteins of less than 20,000 daltons into the buffer, and ribonuclease I was activated. Ribosomes of KA204 liberated a little but much lesser amount of such proteins under the same condition, and ribonuclease I stayed in an inactive state. The livS gene was found to be closely linked to aroA located at 19 min on the Salmonella genetic map. Co-transduction frequency of livS with aroA, and vice versa, ranged from 12 to 55%.