The formation of bacteriophage T7 and T3 lysozymes from inactive precursors

The early genes of the closely related bacteriophages T3 and T7 are transcribed by the host RNA polymerase whereas the late functions are under the control of a phage dependent polymerase, an early enzyme [ 1,2] . However, the regulation of these different transcriptional processes seems to be leaky, since, for example, it was shown that T7 lysozyme is synthesized in vivo as a late and in vitro as an early function [3] . Hagen and Young [3] reported that there is a lag of about 3-4 min between the appearance of T7 lysozyme mRNA and the appearance of active enzyme during T7 development at 30°C. They further showed that this result was due neither to an inhibition of lysozyme activity in early extracts nor to the maturation of the enzyme from an inactive precursor. Here we report data suggesting that, at least in vitro, the T7 and T3 lysozymes are first produced in an inactive form.