Packing of DNA in the head of bacteriophage T2.
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Biomedical subjects
Publications and source records attributed to V M Andreev.
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Phage DNA was accumulated in cells of E. coli B, infected with the phage T4DtsLB3 (gene 42), without the synthesis of late proteins (in the presence of chloramphenicol). Then (stage II), chloramphenicol was removed and further replication of the phage DNA suppressed with hydroxyurea and by simultaneously raising the temperature to 40 degrees. The media M9 or M9 with 1% amino acid were used; the times of addition of chloramphenicol and the hydroxyurea concentration were also varied. It was also shown that in medium M9, at stage II, chiefly early proteins were synthesized. In the medium containing amino acids, at stage II the following was observed: 1) DNA synthesis was entirely suppressed and a degradation of DNA occurred; 2) both early and late proteins were synthesized, with a predominance of the latter; 3) an assembly of the elements of the phage tails and capsids occurred without the neck and flagellum, and a small number of phage particles were also found; 4) the capsids, isolated in a sucrose density gradient after lysis with chloroform, contained the proteins Palt, P20, P23, P24, several unidentified proteins, and did not contain Pwac, P23, and P22, 5) the yield of viable phage varied from 0.05 to 15% per cell. Thus, the entire morphogenesis of T4 phage can occur without accompanying replication of phage DNA.
The kinetics of photoreactions between DNA and psoralen was analysed. A method is described for determining the dependence of the average number of cross-links per base-pair (n) on the fluence of UV-irradiation. This calibration curve allows to specify the conditions of irradiation necessary to obtain any desired value of n.
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Using psoralen for the photochemical cross-linking of DNA chains the authors have demonstrated the formation of conjugated lesions, of both opposite and non-opposite types, in X-irradiated superhelical DNA of PM2 phage. It is suggested that these lesions result from hitting a DNA molecule by a spur.
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