STRUCTURAL-ANALYSIS OF THE RHLE GENE OF EXCHERICHIA-COLI

The E. coli chromosome is known to carry at least five genes, each of which codes for a ''D-E-A-D'' box protein that is presumed to possess an ATP-dependent RNA helicase activity. Four of such genes (srmB, deaD, dbpA and rhlB) were already mapped on the E. coli chromosome and their DNA sequences determined. We here report the complete nucleotide sequence of the remaining rhlE gene located at about 17.8 min on the E. coli genetic map. RhlE protein possesses all of the motifs (I to VI) conserved among prokaryotic and eukaryotic ''D-E-A-D'' proteins and has an arginine-rich carboxyl-terminal region. A null mutant of the rhlE gene was constructed by a new method with a ColE1 plasmid mutant that replicates in RNase HI-deficient bacterial strains, but not in the wild-type strains. The DELTArhlE mutant can grow normally, implying that the rhlE gene product is nonessential for bacterial cell growth.