The isolation and characterization of a sequence-specific endonuclease from Anabaena subcylindrica

Abstract
An endonuclease, AsuI, was isolated from extracts of A. subcylindrica on the basis of gel-electrophoretic analysis of digests of bacteriophage-.lambda. DNA with the partially purified extracts. The enzyme requires Mg2+, but no other cofactors. Endonuclease AsuI recognizes the interrupted tetranucleotide sequence: .**GRAPHIC**. and breaks the phosphodiester bonds indicated by the arrows to leave single-stranded trinucleotide projections at the 5''-termini of the DNA fragments.