Gene 61.3 of bacteriophage t4 is the spackle gene

The bacteriophage T4 e gene encodes lysozyme (e-lysozyme), which releases p rogeny phage after normal infection of Escherichia coli cells. A mutation i n the spackle gene suppresses the defect in e-lysozyme (Emrich, 1968). The spackle gene was mapped between genes 41 and 61, but its precise location h as not previously been determined. In the current study, we constructed an amber mutant of gene 61.3, amST14, by site-directed mutagenesis. The gene 6 1.3 mutant shares phenotypes with spackle mutants: The amST14 mutant forms large plaques with sharp edges and exhibits truncated lysis inhibition, and furthermore, the mutation can suppress the defect in e-lysozyme activity. In addition, cloned gene 61.3 can rescue (by homologous recombination) as w ell as complement the S12 mutation in the spackle gene. These results stron gly suggest that gene 61.3 is the spackle gene. Indeed, the S12 mutant has one base deletion of five in a consecutive A tract in the gene 61.3 coding region, substituting an unrelated 6-amino acid sequence for the 9 C-termina l amino acids in the gene 61.3 protein. The gene 61.3 protein is predicted to localize in the periplasmic space after cleavage of a signal sequence. ( C) 1999 Academic Press.