The Replication of Bacteriophage MS2: V. Proteins Specifically Associated with Infection

Abstract

Uninfected and MS2-infected Escherichia coli spheroplasts, treated with 10 μg/ml. of actinomycin D, were labeled, one with a [^(14)C]amino acid and the other with the corresponding [^3H]amino acid. The resultant lysates were combined, fractionated and the fractions differentially counted. Several protein fractions contained an increased ratio of counts from the infected culture to counts from the uninfected culture. These were: (1) a histidine-labeled fraction with an S value of about 41 s derived from a 13,000 g sediment; (2) a fraction sedimenting at 60 to 80 s and a fraction sedimenting at greater than 81 s, both of which were derived from the 105,000 g sediment (these fractions were observed with leucine or lysine labeling, but not with histidine labeling); (3) a fraction sedimenting at about 6 s from a 105,000 g sediment, labeled with histidine; (4) fractions from the 105,000 g supernatant which were eluted from a DEAE-Sephadex column at 0·22 M-NaCl and 0·26 M-NaCl in pH 7·6 buffer. Also, a fraction was isolated from both infected and uninfected cells, the synthesis of which seemed independent of the presence of actinomycin.

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