Oligoribonuclease is encoded by a highly conserved gene in the 3'-5' exonuclease superfamily

Abstract

Oligoribonuclease, a 3'-to-5' exoribonuclease specific for small oligoribonucleotides, was purified to homogeneity from extracts of Escherichia coli. The purified protein is an alpha2 dimer of 40 kDa. NH2-terminal sequence analysis of the protein identified the gene encoding oligoribonuclease as yjeR (o204a), a previously reported open reading frame located at 94 min on the E. coli chromosome. However, as a consequence of the sequence information, the translation start site of this open reading frame has been revised. Cloning of yjeR led to overexpression of oligoribonuclease activity, and interruption of the cloned gene with a kanamycin resistance cassette eliminated the overexpression. On the basis of these data, we propose that yjeR be renamed orn. Orthologs of oligoribonuclease are present in a wide range of organisms, extending up to humans.

FIG. 1

SDS-PAGE of purified oligoribonuclease. Samples from the Affi-Gel Blue column were concentrated 5- to 10-fold with a Centricon-10 membrane and analyzed by SDS-PAGE on a 12.5% gel. Lane 1, Affi-Gel Blue flowthrough; lane 2, Affi-Gel Blue wash; lane 3, Affi-Gel Blue oligoribonuclease peak activity fraction; lane 4, Affi-Gel Blue fractions before activity peak; lane 5, standards; bovine serum albumin (68,000 Da), ovalbumin (44,000 Da), and chymotrypsinogen (24,500 Da); lane 6, DEAE-Sephadex combined activity peak fractions. The arrow indicates the position of the oligoribonuclease subunit.