double-stranded RNA binding motif of ribonuclease III (RNase III) and similar proteins
RNase III (EC 3.1.26.3; also known as ribonuclease 3) digests double-stranded RNA formed within single-strand substrates, but not RNA-DNA hybrids. It is involved in the processing of rRNA precursors, viral transcripts, some mRNAs, and at least 1 tRNA (metY, a minor form of tRNA-init-Met). It cleaves the 30S primary rRNA transcript to yield the immediate precursors to the 16S and 23S rRNAs. The cleavage can occur in assembled 30S, 50S, and even 70S subunits and is influenced by the presence of ribosomal proteins. The RNase III family also includes the mitochondrion-specific ribosomal protein mL44 subfamily, which is composed of mitochondrial 54S ribosomal protein L3 (MRPL3) and mitochondrial 39S ribosomal protein L44 (MRPL44). Members of this family contain an RNase III domain and a C-terminal double-stranded RNA binding motif (DSRM). DSRM is not sequence specific, but highly specific for dsRNAs of various origin and structure.