Intermediates of Bacteriophage MS2 Assembly In Vivo

Abstract

The in vivo process of virion assembly was studied in rifampin-treated, MS2-infected Escherichia coli during late times of infection-after 18 min postinfection. Differential sucrose gradient sedimentation of infected-cell lysates taken at various times after radioactive labeling indicated a definite temporal order of appearance of phage-specific protein in assembly-related structures. Labeled MS2 protein appears first as a low-molecular-weight peak at the tops of gradients, then as a peak at 40S and as a large number of almost unseparable structures between 40 and 80S, and finally as 80S mature phage particles. During the chase of a short labeling period, radioactive phage protein was found to disappear from gradients in the same temporal order as it appeared; the soluble peak disappears first, followed by the 40 to 70S region. The chased label appears