Prediction and identification of new type holin protein of Escherichia coli phage ECP26

Bacteriophages (phages) infecting specifically target bacteria utilize a unique lysis module known as the holin-endolysin cassette to release progeny. Studies on the phage lytic proteins could contribute to the development of alternatives to antibiotics. Here, we predicted and identified the holin protein of rV5-like phage ECP26 for increasing lytic activity of the phage endolysin. In silico analysis revealed that open reading frame 151 (ORF151) of ECP26 contained two transmembrane domains. Co-expression of endolysin with ORF151 resulted in the cell lysis of Escherichia coli , suggesting that ORF151 protein functioned as the holin that disrupted the cytoplasmic membrane. The putative holin showed a high amino acid homology by more than 80% to the predicted holins of rV5-like phages. Therefore, the holin protein would be helpful for developing efficient lysis strategies with endolysin against gram-negative E. coli .