1) The lysozyme from the bacteriophage T4 eJD7 eJD4, which is a spontaneous revertant of the eJD4 frame shift mutant, has been isolated and purified. Studies on the amino acid sequence of the enzyme showed that its primary structure differs from that of the wild type lysozyme by the substitution of the 140th residue from the amino terminal, viz. Asn, by the Lys-Ile dipeptide. 2) Analysis of the results lead to the conclusion that the eJD4 (one base insertion) frame shift mutation was suppressed by the insertion of two bases at the eJD7 mutation. 3) A previously proposed mechanism of the frame shift mutation could be applied also to the present mutant. 4) The introduction of the basic residue (Lys) caused the decrease of the specific activity of the enzyme to half of that of the wild type.
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