2ND-SITE EVERSION OF A STRUCTURAL DEFECT IN BACTERIOPHAGE-T4 LYSOZYME

A plasmid-borne gene encoding bacteriophage T4 lysozyme with a structu ral mutation, Tyr(161)-Ala, was mutagenized by the use of polymerase c hain reaction, The mutagenized gene was inserted into a specialized ba cteriophage lambda cloning vector that must acquire a functional lysoz yme gene in order to form plaques, Functional variants of the mutant l ysozyme were selected. Three compensatory second-site revertants were obtained: Thr(152)-Met, Lys(43)-Ile, and Thr(151)-Ala. The effects of these mutations are interpreted in light of previous structural and ge netic studies of T4 lysozyme.