The Processive Degradation of Individual Polyribonucleotide Chains

The experiments reported here suggest that Escherichia coli ribonuclease II, an exonuclease, hydrolyzes a given polyribonucleotide chain to completion before releasing a small, resistant oligonucleotide and initiating hydrolysis of another chain. Investigation of the products of hydrolysis of oligo- and polyribonucleotides indicates that enzymatic degradation starts at that end of the chain bearing a 3'-hydroxyl group. The enzyme shows a strong preference for long polymers as substrates, although oligonucleotides are hydrolyzed if present at sufficiently high concentration.