Escherichia coli RNase D: Sequencing of the rnd structural gene and purification of the overexpressed protein

We have determined the nucleotide sequence of a 1.4-kb-pair fragment of the E. coli chromosome that carries the complete rnd gene encoding RNase D, a putative tRNA processing enzyme. The coding region of rnd extends for a total of 1128 nucleotides beginning at an initiator UUG codon and terminating at a UAA codon, and encodes a 375-amino acid polypeptide of 42,679 daltons, consistent with the known size of RNase D. A rapid purification procedure was developed for isolation of RNase D from strains overexpressing the enzyme. The N-terminal sequence and the amino acid composition of the homogenous protein were in excellent agreement with those derived from the sequence of the rnd gene.