Kompetitive Hemmung der Photo-Reaktivierung von uv-inaktivierten T4-Phagen durch stark uv-bestrahlte Phagen-DNA
2014
Harm, Walter | Hillebrandt, Brigitte
Kinetic studies of photo-reactivation (PhR) in uv-inactivated phage T4 v₁ give evidence for a decreased PhR-rate during the first minutes of illumination if additional heavily uv-irradiated phage DNA is present within the bacterial cell. This is considered as due to competition between photoreactivable uv-lesions for the PhR-enzyme molecules. It does not occur if the heavily uv-irradiated DNA received maximum PhR before the addition of the phage whose PhR kinetics is to be studied.The decrease of the PhR-rate depends on the number of competing uv-lesions brought into the cell. The results permit estimating an upper limit for the number of PhR-enzyme molecules present in an E. coli cell, which is about 400. Also by competition experiments it can be tested to what extent phages inactivated by some agent other than UV are still capable of DNA injection. In the case of inactivation by formaldehyde it is shown that only a fraction of the total DNA reaches the interior of the cells.
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