Different specific activities of the monomeric and oligomeric forms of plasmid DNA in transformation of B. subtilis and E. coli. |
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Authors: | Monica Mottes Guido Grandi Vittorio Sgaramella Umberto Canosi Giovanna Morelli and Thomas A Trautner |
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Institution: | (1) Laboratorio di Genetica, Biochrmica ed Evolutionistica del CNR, Via S. Epifanio, 14, I-27100 Pavia, Italy;(2) Farmitalia-C Erba. SpA, Via C. Imbonati, 24, I-20159 Milano;(3) Abt. Trautner, Max-I lanck-Institut für molekulare Genetik, Ihnestraße 63/73, D-1000 Berlin 33;(4) Present address: California Institut of Technology Division of Biology, 156-29-Pasadena, 91125, Cal, USA |
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Abstract: | Summary (1) The low residual transforming activity in preparations of monomeric, supercoiled, circular (CCC) forms of the plasmids pC194 and pHV14 could be attributed to the presence in such isolates of a small number of contaminating multimeric molecules. (2) E. coli derived preparations of pHV14, an in vitro recombinant plasmid capable of replication in both E. coli and B. subtilis, contain oligomeric forms of plasmid DNA in addition to the prevalent monomeric CCC form. The specific transforming activity of pHV14 DNA for E. coli is independent of the degree of oligomerization, whereas in transformation of B. subtilis the specific activity of the purified monomeric CCC molecules is at least four orders of magnitude less than that of the unfractionated preparation. (3) Oligomerization of linearized pHV14 DNA by T4 ligase results in a substantial increase of specific transforming activity when assayed with B. subtilis and causes a decrease when used to transform E. coli. |
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