Alteration of active transport after bacteriophage T5 infection

Abstract

Bacteriophage T5 adsorption immediately followed by injection of the first-step-transfer DNA segment produces alterations in the bacterial membrane which reduce the uptake of amino acids and of onitrophenyl-3-D-galactopyranoside. Concomitantly, intracellular ATP is hydrolyzed. The extent of inhibition of uptake and of ATP hydrolysis is cooperatively increased with the multiplicity of infection. Inhibition of active transport at a high multiplicity of infection (>3) is also observed after the second step of DNA injection. In contrast, at low multiplicities of infection, phage proteins are able to enhance amino acid uptake. Infection of su-bacteria with amber mutants in the first-step-transfer DNA suggests that protein Al is implicated in this enhancement.Coliphage T5 adsorbs to a specific outer membrane receptor which contains the product of the gene tonA (7). Immediately after irreversible binding to the outer membrane, the bacteriophage first injects 8% of the length of its DNA molecule (first-step-transfer [FST] DNA) into the cytoplasm (10, 22).These events trigger important modifications in the bacterial envelope. Hantke and Braun (16) and Braun and Oldmixon (6) have observed a large perturbation in the fluorescence of ANS (8-anilino-1-naphthalene sulfonate) which may be attributed to a local increase in hydrophobicity leading to a new arrangement of membrane components. Simultaneously, cations like K+ and Mg2+ are extruded from the bacteria (15,24). This extrusion is a general response to phage adsorption and is also observed after T2, T3, and T7 infection (26,27). Concomitantly, a transient wave of depolarization-repolarization of the cytoplasmic membrane without variation of the ApH accompanies the first steps of T5 phage infection, as demonstrated by Labedan and Letellier with cyanine dye fluorescence (20).The injection of the second part of the phage DNA (second-step-transfer [SST] DNA) needs the presence of both Al and A2 pre-early proteins encoded by the FST segment (21). The Al and A2 proteins are located in both the inner and the outer membranes of infected bacteria (5,9,11,28). A pre-early polypeptide of 30,000 daltons, not genetically identified, appears also in the inner membrane (5). The insertion of these proteins into the bacterial membrane may be responsible for later changes observed both by Hantke and Braun (16) with ANS fluorescence and by Glenn and Duckworth (14) with membrane-bound NPN (N-phenyl-1naphthylamine) fluorescence.Furthermore, soon after T5 infection, amino acid accumulation, as well as thiomethylgalactoside transport, is transiently inhibited (8,13). On the other hand, net uptake of amethylglucoside is stimnulated (13). Ten minutes after infection, the inhibited transports return to the levels of uptake exhibited by uninfected bacteria (13). These modifications of different metabolite transport systems indicate that membrane changes occur during the first steps of phage development.In this paper, we show that proline and glutamine uptake and ONPG (o-nitrophenyl-o-D-galactopyran...