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The lytic enzyme of bacteriophage PRD1 is associated with the viral membrane
Pia S Rydman1, Dennis H Bamford
1Department of Biosciences and Institute of Biotechnology, Viikki Biocenter, University of Helsinki, 00014 University of Helsinki, Finland.
Abstract:
Bacteriophage PRD1 encodes two proteins (P7 and P15) that are associated with a muralytic activity. Protein P15 is a soluble beta-1,4-N-acetylmuramidase that causes phage-induced host cell lysis. We demonstrate here that P15 is also a structural component of the PRD1 virion and that it is connected to the phage membrane. Small viral membrane proteins P20 and P22 modulate incorporation of P15 into the virion and may connect it to the phage membrane. The principal muralytic protein involved in PRD1 DNA entry seems to be the putative lytic transglycosylase protein P7, as the absence of protein P15 did not delay initiation of phage DNA replication in the virus-host system used. The incorporation of two different lytic enzymes into virions may reflect the broad host range of bacteriophage PRD1.
Insights
Bacteriophage PRD1 utilizes two lytic enzymes, P7 and P15, for host cell lysis and DNA entry. P15 is a structural virion component, while P7 appears crucial for DNA translocation, reflecting PRD1's broad host range.
Area of Science:
- Microbiology
- Virology
- Molecular Biology
Background:
- Bacteriophage PRD1 possesses muralytic activity, essential for its life cycle.
- Two proteins, P7 and P15, have been implicated in this muralytic activity.
Purpose of the Study:
- To elucidate the roles of bacteriophage PRD1 proteins P7 and P15 in virion structure and function.
- To investigate the specific contributions of P7 and P15 to phage-induced host cell lysis and DNA entry.
Main Methods:
- Biochemical analysis of PRD1 proteins P7 and P15.
- Structural investigation of the PRD1 virion.
- Functional assays using virus-host systems to assess DNA replication and entry.
Main Results:
- Protein P15, a beta-1,4-N-acetylmuramidase, is a structural component of the PRD1 virion, linked to the phage membrane.
- Small viral membrane proteins P20 and P22 regulate P15 incorporation and membrane attachment.
- Protein P7, a putative lytic transglycosylase, is identified as the primary enzyme for PRD1 DNA entry.
- Absence of P15 did not impede DNA replication initiation, suggesting P7's dominant role in DNA entry.
Conclusions:
- Bacteriophage PRD1 virions incorporate distinct lytic enzymes (P7 and P15) with specialized functions.
- P15 contributes to host cell lysis and virion structure, while P7 is critical for phage DNA entry.
- The dual lytic enzyme system may contribute to bacteriophage PRD1's broad host range.