Isolation and characterization of the bacteriophage T4 tail-associated lysozyme

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Abstract
Direct evidence was obtained that the tail-associated lysozyme of bacteriophage T4 (tail-lysozyme) is gp5, which is a protein component of the hub of the baseplate. Tails were treated with 3 M guanidine hydrochloride containing 1% Triton X-100, and the tail-lysozyme was separated from other tail components by preparative isoelectric focusing electrophoresis as a peak with an isoelectric point of 8.4. The MW as determined from sodium dodecyl sulfate electrophoresis was 42,000. The tail-lysozyme was unambiguously identified as gp5 when the position of the lysozyme was compared with that of gp5 of tube-baseplates from 5ts1/23amH11/eL1a infected Escherichia coli cells by 2-dimensional gel electrophoresis. The tail-lysozyme has N-acetylmuramidase activity and the same substrate specificity as gene e lysozyme; the optimum pH is .apprx. 5.8, about 1 pH unit lower than for the e lysozyme. The tail-lysozyme is assumed to play an essential role in locally digesting the peptidoglycan layer to let the tube penetrate into the periplasmic space. The tail-lysozyme is presumably also responsible for lysis-from-without.