Identification of an amber uvrC mutant in Escherichia coli K-12.

An Escherichia coli K-12 ultraviolet (UV)-sensitive mutant KMBL92 (dar-4) was identified as an amber uvrC mutant. In a suppressor-free genetic background it showed high sensitivity to UV, no reactivation of UV-irradiated λ phage and positive Weigle reactivation, whereas upon introduction of a suppressor mutation it exhibited moderate resistance to UV, intermediate capacity for host-cell reactivation and no Weigle reactivation. Other properties, like DNA degradation during post-UV incubation and frequencies of UV-induced mutations in bacteria and bacteriophage λ, were similar to those of a uvrC mutant.