SUPPRESSION OF A LAC O-O MUTATION IN ESCHERICHIA COLI.

Schwartz, Norman M. (Yale University, New Haven, Conn.). Suppression of a lac o degrees mutation in Escherichia coli. J. Bacteriol. 88:996-1001. 1964.-A class of pro(-) markers which can be cotransduced with lac map close to the i side of the lac region. The relative order of markers transferred by Hfr H is thr leu proA proB lac proC ade. Nine of ten slowgrowing lactose-utilizing revertants of a lac o degrees mutant are suppressed mutants. The time of entry of su-lac o-5 from an Hfr H derivative is 27 min. Su-lac o-5 is separated from the lac region by a 10-min interval. Su-lac o-5 is unstable, restores 7% of the wild-type level of beta-galactosidase activity, suppresses a try(-) mutation, and has a deleterious effect upon growth rate. The primary lac o degrees mutation is interpreted as being a z(-) polarity mutation which constitutes nonsense. Su-lac o-5 could act at the level of messenger ribonucleic acid translation converting nonsense to sense by promoting mistakes in protein synthesis.