Abstract
The pnd gene of R plasmid R483, like the srnB gene of the F plasmid, increases the degradation of stable RNA in Escherichia coli. The nucleotide sequence of the pnd locus was determined and compared with that of the srnB locus. The genes have open reading frames that are 54% homologous, and both have an upstream inverted repeat sequence. The pnd gene expression seems to decrease the osmotic barrier of the cytoplasmic membrane, since no plasmolytic vacuoles were formed in the cells carrying the gene when the cells were exposed to hypertonic sucrose solution. This result suggests that RNase I in the periplasm passes through the altered membrane to degrade stable RNA in the cytoplasm.
