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Formation in vitro of Infective Joint Molecules of λ DNA by T4 Gene-32 Protein
Wilfried Wackernagel and Charles M. Radding
Proceedings of the National Academy of Sciences of the United States of America
Vol. 71, No. 2 (Feb., 1974), pp. 431-435
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/62790
Page Count: 5
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Half molecules of λ DNA that had been partially digested by λ exonuclease to expose homologous single strands were rejoined by the action of T4 gene-32 protein at 37 degrees in the presence of Mg++. Measurements of infectivity in su- spheroplasts and sedimentation in sucrose demonstrated the formation of sus+ joint molecules from two preparations of sheared λ DNA that carried sus mutations at opposite ends of the genome. The biological activity of joint molecules made by annealing at 75 degrees was diminished by the addition of the gene-32 protein in the absence of Mg++, and largely restored by the subsequent addition of Mg++. The specific infectivity of joint molecules made by gene-32 protein at 37 degrees was similar to that of joint molecules made by annealing at 75 degrees. The experimental system described provides a possible model for simulating early steps in genetic recombination.
Proceedings of the National Academy of Sciences of the United States of America © 1974 National Academy of Sciences