radC102 of Escherichia coli is an allele of recG

The radC102 mutation causes mild UV and X-ray sensitivity and was mapped pr eviously to near pyrE and recG at 82 min on the Escherichia coli chromosome (I, Felzenszwalb, N. J. Sargentini, and K. C. Smith, Radiat. Res. 97:615-6 25, 1984), We report that radC102 has two striking phenotypes characteristi c of recG mutations. First, it causes dramatically increased RecA-dependent mutation in a stationary-phase mutation assay, Second, it causes extreme U V sensitivity in combination with ruv mutations affecting the RuvABC Hollid ay junction resolution system. DNA sequencing of the radC and recG genes in radC102 strains revealed that the radC102 mutation creates a stop codon in recG that is predicted to truncate the RecG protein at 410 of 603 amino ac ids. A lo cv-copy-number plasmid carrying the radC(+) gene did not affect t he UV sensitivity of a wild-type strain, a radC102 strain, or a recG258::Tn 10mini-kan strain. We conclude that radC102 is an allele of recG and that t he function of the RadC protein remains to be determined.