Activity (A) and thermostability (B) of V. vulnificus nuclease on various substrates. (A) Phage λ DNA (500 ng; lanes 1 to 3), pUC19 DNA (500 ng; lanes 4 to 6), and E. coli rRNA (4 μg; lanes 7 to 9) were treated with the periplasmic fraction (5 μl) of DH5α(pSI014) (lanes 3, 6, and 9) or that of DH5α(pUC19) (lanes 2, 5, and 8) for 30 min at 37°C. Lanes 1, 4, and 7 are the untreated substrates. (B) Periplasmic fraction of DH5α(pSI014) was heated at 37°C (lane 1), 50°C (lane 2), 70°C (lane 3), 90°C (lane 4), and 100°C (lane 5) for 30 min and then used to digest either λ DNA or rRNA in conditions described above. Digests were examined by agarose (0.8%) gel electrophoresis. Lanes C contain untreated substrate. pSI014 was a pUC19 derivative containing the vvn gene.