Exoribonuclease that catalyzes the last steps of 5S, 16S and 23S rRNA 5'-end maturation. Removes 3 nucleotides (nt) from the 5' end of 5S, 16S and 23S rRNA precursors to generate the mature 5' ends. Precursors with longer extensions are not processed (7 nt at the 5' end of pre-23S rRNA or 66 nt at the 5'-end of 16S rRNA are not processed). 5S and 23S rRNA maturation occurs more efficiently and accurately on ribosomal particles as compared to free RNA; the enzyme overdigests free RNA but generates the correct 5'-end in ribosomes from rnm deletion strains (PubMed:32343306). Efficiently catalyzes the hydrolysis of the 3'-phosphate from 3',5'-bis-phosphonucleotides as well as the successive hydrolysis of 5'-phosphomononucleotides from the 5'-end of short pieces of RNA and DNA, with no specificity toward the identity of the nucleotide base. Is more efficient at hydrolyzing RNA oligonucleotides than DNA oligonucleotides. This enzyme can also hydrolyze annealed DNA duplexes, albeit at a catalytic efficiency approximately 10-fold lower than that of the corresponding single-stranded oligonucleotides. a ribonucleoside 3',5'-bisphosphate + H2O = a ribonucleoside 5'-phosphate + phosphate Binds 1 Mn(2+) ion per subunit (PubMed:25871919). However, the sequence similarity to CV_1693 from C.violaceum tends to indicate a trinuclear metal center. kcat is 9.9 sec(-1) with pAp as substrate. kcat is 5.6 sec(-1) with 2'-deoxy-pAp as substrate. kcat is 6.0 sec(-1) with pCp (2'5'/3'5' mixture) as substrate. kcat is 1.9 sec(-1) with 2'-deoxy-pCp as substrate. kcat is 5.5 sec(-1) with pGp (2'5'/3'5' mixture) as substrate. kcat is 1.7 sec(-1) with 2'-deoxy-pGp as substrate. kcat is 4.7 sec(-1) with pUp as substrate. kcat is 2.1 sec(-1) with 2'-deoxy-pUp as substrate. kcat is 1.6 sec(-1) with 2'-deoxy-pTp as substrate. kcat is 3.3 sec(-1) with 2'-deoxy-pIp as substrate. kcat is 0.22 sec(-1) with 3'-AMP as substrate. kcat is 0.60 sec(-1) with p(Gp)G as substrate. kcat is 14 sec(-1) with p(Ap)A as substrate. kcat is 3.8 sec(-1) with p(Ap)(2)A as substrate. kcat is 3.6 sec(-1) with p(Ap)(3)A as substrate. kcat is 2.7 sec(-1) with p(Ap)(4)A as substrate. kcat is 2.5 sec(-1) with p(dAp)dA as substrate. kcat is 0.72 sec(-1) with p(dAp)(2)dA as substrate. kcat is 1.20 sec(-1) with p(dAp)(3)dA as substrate. kcat is 0.79 sec(-1) with p(dAp)(4)dA as substrate. None of the 3 rRNAs are correctly processed at their 5' ends, each accumulates a precursor with 3 extra nucleotides. Since E.coli possesses another enzyme, CysQ, which has been demonstrated to catalyze the hydrolysis of 3',5'-pAp to 5'-AMP and phosphate during sulfur assimilation, it seems therefore unlikely that the hydrolysis of 3',5'-bis-phosphonucleotides will be the primary physiological function of YciV. Was originally suggested to be involved in tryptophan metabolism, thus the gene synonym trpH. Belongs to the PHP family. TrpH/YciV subfamily.