HgiAI: a restriction endonuclease from Herpetosiphon giganteus HP1023.

A new class II restriction endonuclease, HgiAI has been partially purified from Herpetosiphon giganteus HP1023. The enzyme activity has been characterized and shown to recognize the family of related hexanucleotide sequences (Formula: see text) where the second and fifth nucleotide pairs are A:T pairs in either orientation. Cleavage occurs as shown, to give DNA fragments with 3'-terminal tetranucleotide extensions. The recognition sites of the enzymes SacI and SstI (Formula: see text) form a subset of the recognition site of HgiAI. One of the four possible tetranucleotide 3'-extensions (cohesive ends), generated by HgiAI is identical with those generated by SacI and SstI, another is identical with that of PstI. HgiAI should be useful for molecular cloning.