Properties of the Exonucleolytic Activities of the Micrococcus luteus Deoxyribonucleic Acid Polymerase

The Micrococcus luteus DNA polymerase possesses a 5' to 3' exonuclease activity which is an integral part of the polymerase protein. The 5' to 3' exonuclease preferentially degrades double stranded DNA and yields a mixture of mononucleotides, dinucleotides, and trinucleotides as products. This spectrum of products is found for double stranded substrates of the following types: poly(deoxypurine)·poly(deoxypyrimidine); poly(deoxypurine-deoxypyrimidine)·poly(deoxypurine-deoxypyrimidine) as well as native DNA. The relative proportion of these degradation products depends on the base sequence of the DNA substrate and the reaction pH. The M. luteus DNA polymerase also possesses a 3' to 5' exonuclease activity which yields mononucleotides as products and is approximately 10 times more active than the 5' to 3' exonuclease with a single stranded poly(dT) substrate.