A peptidoglycan hydrolase motif within the mycobacteriophage TM4 tape measure protein promotes efficient infection of stationary phase cells.

Mariana Piuri,Graham F Hatfull

doi:10.1111/j.1365-2958.2006.05473.x

Abstract

The predominant morphotype of mycobacteriophage virions has a DNA-containing capsid attached to a long flexible non-contractile tail, features characteristic of the Siphoviridae. Within these phage genomes the tape measure protein (tmp) gene can be readily identified due to the well-established relationship between the length of the gene and the length of the phage tail – because these phages typically have long tails, the tmp gene is usually the largest gene in the genome. Many of these mycobacteriophage Tmp's contain small motifs with sequence similarity to host proteins. One of these motifs (motif 1) corresponds to the Rpf proteins that have lysozyme activity and function to stimulate growth of dormant bacteria, while the others (motifs 2 and 3) are related to proteins of unknown function, although some of the related proteins of the host are predicted to be involved in cell wall catabolism. We show here that motif 3-containing proteins have peptidoglycan-hydrolysing activity and that while this activity is not required for phage viability, it facilitates efficient infection and DNA injection into stationary phase cells. Tmp's of mycobacteriophages may thus have acquired these motifs in order to avoid a selective disadvantage that results from changes in peptidoglycan in non-growing cells.

Highlights

All bacteriophages are posed with the common problem of how to accomplish injection of their genomes across the walls and membranes of their host bacterial cellsAccepted 9 October, 2006. *For correspondence
The predominant morphotype of mycobacteriophage virions has a DNA-containing capsid attached to a long flexible non-contractile tail, features characteristic of the Siphoviridae
Within these phage genomes the tape measure protein gene can be readily identified due to the well-established relationship between the length of the gene and the length of the phage tail – because these phages typically have long tails, the tmp gene is usually the largest gene in the genome. Many of these mycobacteriophage tape measure proteins (Tmp’s) contain small motifs with sequence similarity to host proteins. One of these motifs corresponds to the Resuscitation Promoting Factor (Rpf) proteins that have lysozyme activity and function to stimulate growth of dormant bacteria, while the others are related to proteins of unknown function, some of the related proteins of the host are predicted to be involved in cell wall catabolism

Summary

Introduction

All bacteriophages are posed with the common problem of how to accomplish injection of their genomes across the walls and membranes of their host bacterial cellsAccepted 9 October, 2006. *For correspondence. The virion particles of several phages of Gramnegative hosts have been shown to contain hydrolytic activities targeted against peptidoglycan; for example, virions of T4, T7, f6 and PRD1 contain either lysozyme, transglycosylase or endopeptidase activities (Nakagawa et al, 1985; Caldentey and Bamford, 1992; Moak and Molineux, 2000; Rydman and Bamford, 2000; Kanamaru et al, 2002). The location of these functions within the virions is varied. While the specific roles of these peptidoglycan-degrading activities may differ somewhat, it is likely that they share a common function in facilitating efficient infection of host cells, either by enabling access to the cytoplasmic membrane or mediating transfer of virion DNA from the capsid to the cellular cytoplasm

Results

Discussion

Conclusion