Practice question

RNase D encoded by rnd gene in E. coli is hydrolytic 3' to 5' exonuclease requiring Mg2+ that digests single-stranded RNA from free 3' hydroxyl. It participates in final trimming of tRNA precursors, 5S rRNA, and other stable RNAs after initial endonucleolytic cuts. Unlike endonucleases RNase III, E and P which cut internally, RNase D nibbles one nucleotide at a time until stopped by stable secondary structure like acceptor stem. Its distributive action provides proofreading precision, preventing over-digestion and ensuring accurate mature ends.