Structure and synthesis of a lipid-containing bacteriophage : II. Alterations in cytoplasmic and membrane-bound enzymes during replication of bacteriophage PM2

Abstract

The specific activity of all membrane-bound enzymes studied decreased during infection of Pseudomonas BAL-31 with the lipid bacteriophage PM2. NADH oxidase, nitro blue tetrazolium chloride reductase, succinic dehydrogenase, and Mg²⁺-dependent ATPase, all involved in oxidative phosphorylation, decreased in specific activity from the start of infection. Glucose phosphotransferase started to decrease rapidly in specific activity only at 10 min after infection (p.i.). Alkaline phosphatase, which presumably lies outside the cell membrane, decreased in a manner similar to the enzymes of oxidative phosphorylation, but not as much. In contrast, two cytoplasmic enzymes, hexokinase and glucose-6-phosphate dehydrogenase, increased in specific activity after infection, reaching a peak of twice the specific activity of uninfected cells at 30 min p.i. The overall rate of protein synthesis in control and infected cells was the same, at least until the commencement of cell lysis at about 60 min p.i. Whereas the bulk of cellular proteins labeled before infection was stable until about 60 min p.i., the specific radioactivity of prelabeled membrane-bound proteins decreased after infection. The latter observation led to the present working hypothesis: namely, that virus-specific proteins are inserted into the cellular membrane; this may or may not be accompanied by the displacement of some normal cellular membrane proteins. The altered cellular membranes, containing virus-specific proteins, may then form the outer shell of the virion.