Preparation and Specificity of Endonuclease IV Induced by Bacteriophage T4

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Abstract
Bacteriophage-T4-induced endonuclease IV suitable for DNA sequence analysis was prepared by a modified and easily reproducible method. The specificity of T4-induced endonuclease IV was investigated in order to verify whether this enzyme exhibits a single nucleotide recognition or a short sequence recognition. The 5''-terminal dinucleotides and 3''-terminal nucleotides of oligonucleotides released by T4-induced endonuclease IV from 3 single-stranded DNAs (from bacteriophages .PHI.X174, fd, M 13) were analyzed. In different DNAs, 74-82% of the 5''-terminal dinucleotides end in 5''-deoxycytidylic acid; small but significant levels of several dinucleotides ending in 5''-deoxyadenylic acid, 5''-thymidylic acid and 5''-deoxyguanylic acid are also found. As far as 3''-terminal nucleotides are concerned, all nucleotides are present with a large predominance of thymidylic acid. T4-induced endonuclease IV apparently recognizes short nucleotide sequences like all other DNases investigated so far. The spectrum of such sequences, is however, very narrow.