Cloning and Sequencing of the rph Gene Encoding RNase PH from Legionella pneumophila

Legionella pneumophila, the cause of Legionnaires' disease, is able to survive intracellularly in eukaryotic cells such as monocytes, macrophages, and protozoan organisms. During protein biosynthesis, the rph gene encodes ribonuclease (RNase) PH which functions as a phosphorolytic nuclease that removes nucleotides following the CCA terminus of tRNA and as a nucleotidyl-transferase which adds nucleotides to the ends of RNA molecules by using nucleoside diphosphates as substrates. In this study, the rph gene was screened in pUC19 library employing a DNA probe which was constructed from PCR based on a consensus pattern of multiple alignment of RNase PH. The encoded protein consists of 235 amino acid residues with a calculated molecular weight of 26,112 Daltons. The RNase PH signature domains are completely conserved.