Ion channels are likely to be involved in the two steps of phage T5 DNA penetration into Escherichia coli cells.

P Boulanger,L Letellier

doi:10.1016/s0021-9258(19)50710-4

Abstract

Phage T5 injects its DNA into Escherichia coli cells in two steps; 8% of the chromosome is first injected, and then there is a pause during which proteins encoded by this DNA fragment are synthesized allowing the remaining DNA to be injected. Using a potassium-selective electrode, we show that the injection of the two DNA fragments is associated with an efflux in two steps, of cytoplasmic potassium. The rate of efflux is linearly related to the number of added phages suggesting that each phage induces the formation of at least one channel in the inner membrane. The first efflux occurs even in depolarized cells suggesting that the insertion and the opening of the channel can take place in the absence of the electrochemical gradient of protons (delta mu H+). The channel is in a closed configuration during the time required for the synthesis of the phage-encoded proteins; this closing and the second efflux are prevented by the depolarization of the cell. The insertion of the channel in the inner membrane requires a fluid membrane. The results obtained suggest that the function of this channel is to translocate phage T5 DNA.

Highlights

Selective electrode, we show that the injection of the two DNA fragmentsis associated with anefflux in two steps, of cytoplasmic potassium
This hypothesis is based on the observation that and arrested at the FstSaTge by infecting in abuffer without additional energy sources or in the presence of chloramphenicol; under these conditions, the DNA molecule remains in continuity between the cytoplasm and thecapsid (Labedan et al, 1973)
Dry weight (Fig. 1).Addition of phage T5 ata multiplicity of infection (MOI) of three phages per bacteria resulted in a first K+ efflux after a lag time of20 s lasting about 2 min. 4 min later a second effluxstarted which lasted about 5

Summary

Introduction

Selective electrode, we show that the injection of the two DNA fragmentsis associated with anefflux in two steps, of cytoplasmic potassium. Addition of chloramphenicol (50 pglml), which prevents the synthesis of proteins A1 and A2 required for SST DNA injection (McCorquodaleand Warner, 1988),either before the first efflux or at its end, totally prevented the second efflux (Fig. 1).The same one-step efflux wasalso observed whenthe phage buffer did not contain an additional energy source(data not shown).

Results

Conclusion