This an expressed but non-active exoribonuclease allele (PubMed:8501045). The catalytically inactive protein translated in strain K12 MG1655 inhibits the 5'-processing of primary pre-tRNAs with short (<5 nucleotide) leaders in a dominant-negative effect when RNA pyrophosphohydrolase (rppH) is also inactive; perhaps inactive Rph inhibits interaction with RNase P which is exacerbated when RppH cannot cleave the triphosphate of the primary transcript (PubMed:28808133). Homodimer (By similarity). No interaction between the inactive protein and RppH or RNase P was detected by immunoprecipitation (PubMed:28808133). The catalytically inactive protein is present at significantly lower levels than restored wild-type protein (at protein level) (PubMed:28808133). When the gene is deleted the strain no longer inhibits 5'-processing of pre-tRNAs with short (<5 nucleotide) leaders in the absence of rppH (PubMed:28808133). The truncated allele encoded by this protein has a slight growth defect, which is slightly exacerbated when combined with an rppH deletion (PubMed:28808133). The truncated allele suppresses the loss of viability conferred by deletion of RNase 2 (rnb) during stationary phase at 31 and 42 degrees Celsius or starvation at 42 degrees Celsius (PubMed:28625967). The gene in K12 strains MG1655 and W3110 (and also other derivatives of K12 W1485) has a frameshift mutation that leads to loss of activity, although the protein is translated. Thus in those strains rph is an expressed, catalytically inactive protein (PubMed:8501045). In strain K12 / MG1655(Seq)* the wild-type protein has been restored (PubMed:21135037, PubMed:27298395, PubMed:28625967). For the functional protein without the frameshift mutation see AC P0CG18. The (restored) wild-type protein plays a significant role in tRNA 3'-end maturation when a C nucleotide follows the mature CCA terminus (PubMed:28808133). Wild-type (restored) protein also plays a critical role in initiating 16S rRNA degradation (leading to ribosome degradation) during starvation, but not in rRNA quality control during steady state growth (PubMed:21135037, PubMed:27298395). The wild-type (restored) protein is rapidly turned over at 42 degrees Celsius during starvation, but not at 31 degrees Celsius with or without starvation; in the absence of RNase 2 (rnb) protein levels do not decline (at protein level) (PubMed:28625967). Belongs to the RNase PH family.