Inability of Escherichia coli B to Incorporate Added Deoxycytidine, Deoxyadenosine, and Deoxyguanosine into DNA.

It is known that Escherichia coli can incorporate labeled thymidme into its DNA, but it has not been previously possible to measure the incorporation of the other deoxyribonucleosides deoxycytidine, deoxyadenosine, and deoxyguanosine because of degradation of these compounds. The present experiments utilize a mutant of E. coli B lacking deoxyribonucleoside-catabolizing enzymes. This strain, OK441, has mutations affecting the following enzymes: thymidine phosphorylase, purine nucleoside phosphorylase, cytidine deaminase, and adenosine deaminase. The results with OK441 show that E. coli, in contrast to lactobacilli and mammalian cells, does not incorporate any deoxyribonucleoside other than thymidine into its DNA. E. coli may be unable to phosphorylate deoxycytidine, deoxyadenosine, and deoxyguanosine. In agreement. with this suggestion, only thymidine kinase but no other deoxyribonucleotide kinase could be detected in extracts of OK441. [ABSTRACT FROM AUTHOR]

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