Bacteriophage uses cell lysis system to release their progeny after multiplication inside host bacteria. Bacterial lysis by phages can be accomplished by two different ways; i) peptidoglycan degradation by a holin-endolysin system found in most double-stranded DNA phages or ii) inhibition of peptidoglycan synthesis seen in single-stranded RNA or DNA phages. In this study, unusual lysis mechanism of a putative lysis protein from a double-stranded DNA containing phage BSPM4 was examined. Genome sequencing and bioinformatics analysis revealed that BSPM4 contained two putative lysis proteins named as LysA and LysB, both of which are not homologous to the known holin and endolysin. However, only LysA caused cell lysis when expressed in E. coli system. Domain analysis showed that LysA is a membrane protein having an apparent transmembrane domain and transmembrane topology prediction suggested that LysA is a peripheral membrane protein anchored to the cytoplasmic membrane by the transmembrane domain. Interestingly, cell lysis was prevented when LysA was co-expressed with penicillin-binding protein 2 (PBP2), a transpeptidase involved in peptidoglycan synthesis at the periplasm, suggesting that LysA might cause cell lysis by inhibiting PBP2 function.