Isolation and characterization of two sequence-specific endonucleases from Anabaena variabilis

Abstract

Two endonucleases, AvaI and AvaII, were isolated from Anabaena variabilis on the basis of their ability to make a limited number of breaks at specific points in bacteriophage λ DNA. Neither enzyme has cofactor requirements beyond Mg2+. Endonuclease AvaI makes eight breaks in the phage λ chromosome at which the 5'-terminal sequence is pPy-C-G-N. AvaII endonuclease cuts phage λ DNA more extensively, yielding fragments with the 5'-terminal sequence G-T-C-N or G-A-C-N. Neither enzyme generates cohesive ends.