Practice question

In Escherichia coli, seven rrn operons produce about 30S primary precursor containing leader, 16S, spacer tRNAs, 23S, 5S and trailer. Maturation initiates with RNase III, a Mg2+-dependent double-strand specific endoribonuclease that cleaves long inverted repeat stems flanking 16S and 23S, co-transcriptionally. Cleavage liberates pre-16S 17S, pre-23S and 9S 5S precursors carrying extra nucleotides at both ends. Subsequent processing by RNase E, RNase G, RNase PH, RNase T, PNPase removes leaders and trailers, generating mature termini essential for subunit assembly and translation activity.