Isolation and characterization of a type II restriction endonuclease fromStreptococcus thermophilus

A type II restriction endonuclease Sth1341 was isolated from Streptococcus thermophilus strain 134. The enzyme is an isoschizomer of HpaII. The restriction endonuclease is most active at Mg(II) ⩾5 mM; in the pH range of 7.5–8; temperature of 50°–55°C; and (KCl) or (NaCl) below 100 mM. Double digestion and ligation experiments showed that Sth1341 apparently recognized and cleaves DNA at the sequence C1CGG to produce two-base, 5′-protruding ends.