An Amber Suppressor of Escherichia coli Strain KO1

The suppression characteristics of Escherichia coli strain KO1 have been investigated. The growth patterns of nonsense mutants of RNA (GA and f2) and DNA (λ and T4) phages suggested that KO1 carried an amber, but not ochre or opal suppressors. The comparison of KO1 with previously identified amber suppressors indicated that KO1 differed from su1, su3 and su6 in its suppression pattern. KO1 and su2 shared some properties in common, for instance, their ability to suppress GA amber mutants with one exception (amN20) and the restriction of suppression capacity by the str^r mutation. However, the suppression efficiency of KO1 (48%) was about three times that of su2 (18%). A possibility that KO1 contained a new amber suppressor is discussed.