Identification of the gene for DNA helicase II of Escherichia coli

Abstract

Using a modification of the solid-phase radioimmune assay of Broome and Gilbert to screen the plaques of .lambda. recombinant phages for the presence of an elevated level of helicase-II-specific antigen, one identified the gene for helicase II in a library of E. coli DNA. The DNA selected was subcloned from .lambda. into plasmid vectors; restriction analysis located the DNA region encoding helicase II in a PvuII fragment identical in size (2900 base pairs) and restriction pattern to that which contains the uvrD gene. Plasmids carrying this DNA fragment complemented the increased sensitivity to UV irradiation and the mutator phenotype of uvrD mutants. Mutant cells (uvrD502) were found to liberate no helicase II activity upon extraction. Following transformation with the cloned DNA, active helicase II was recovered from the mutant cells. These results support the view that helicase II is encoded by uvrD.