Mutants of Escherichia coli B/r Defective in Deoxyribonucleic Acid Initiation: dnaI, a New Gene for Replication
Abstract
Mutants of Escherichia coli B/r Defective in Deoxyribonucleic Acid Initiation: dnaI , a New Gene for Replication D. Beyersmann 1 , W. Messer and M. Schlicht a Max Planck Institut für Molekulare Genetik, Berlin, West Germany ABSTRACT Mutagenized E. coli B/r cells were subjected to a procedure designed to select mutants temperature-sensitive for initiation of deoxyribonucleic acid (DNA) replication. Seventeen mutants exhibiting limited residual DNA synthesis at 42 C were obtained and the dna − sites were mapped genetically. Sixteen of the sites map near dnaA, dnaB , and dnaC . One mutant ( dna-208 ) maps in a new location between the trp and his genes. We propose to call this mutant dnaI208 . In complementation experiments dnaC + and dnaI + were dominant to dnaC − and dnaI − alleles, respectively. However, dnaA − was dominant to the wild-type allele dnaA + . All dnaA mutants and four out of six dnaC mutants could be suppressed by F factor integration. The pattern of suppression was specific for each mutant.