Exonuclease I, E. coli

Applications

Removal of residual ssDNA, including oligos, from reaction mixes.
Removal of ssDNA from nucleic acid mixtures.

Exonuclease I digests ssDNA in a 3´→5´ direction,^1-3 but does not digest dsDNA. Although it requires the presence of magnesium and a free 3´-hydroxyl terminus for activity, it is active under a wide variety of buffer conditions and can be added directly into most reaction mixes. Exonuclease I can be heat-inactivated by incubation at 80°C for 15 minutes.

Unit Definition: One unit of Exonuclease I catalyzes the release of 10 nmol of acid-soluble nucleotides from heat-denatured calf thymus DNA in 30 minutes at 37°C under standard assay conditions.

Storage Buffer: 50% glycerol containing 50 mM Tris-HCl (pH 7.5), 0.1 M NaCl, 0.1 mM EDTA, 1 mM DTT, and 0.1% Triton® X-100.

Quality Control: Exonuclease I is tested in degradation of ssDNA and is free of detectable RNase, endonuclease, and doublestranded exonuclease activities.

References

Lehman, I.R. and Nussbaum, A.L. (1964) J. Biol. Chem. 239, 2628.
Kushner, S.R. et al. (1971) Proc. Natl. Acad. Sci. USA 68, 824.
Kushner, S.R. et al. (1972) Proc. Natl. Acad. Sci. USA 69, 1366.

Figure 1. Specificity of Exonuclease I for ssDNA. 200 ng of EcoR I-linearized pUC19 dsDNA and 1 µg of a 100-mer ssDNA oligo were mixed in 1X TA Buffer and incubated at 37°C for 20 min in the absence or presence of 10 units of Exonuclease I. As seen on this 1% agarose gel, Exonuclease I completely digested the linear ssDNA oligo, but left the linearized plasmid dsDNA intact. Lane 1, size markers; Lane 2, minus Exo I; Lane 3, plus Exo I.

Ordering

Catalog No.		Concentration		Size

X40501K	20 U/µl	1,000 Units
X40505K	20 U/µl	5,000 Units
X40520K	20 U/µl	20,000 Units

Note: Catalogue number X40501K has been discontinued, effective from August 2014. This product is available only until stocks last.