16 MAURICE J. BESSMAN 



specificity seems to reside in the structure of the base and does not 

 involve the sugar moiety. The name deoxynucleotide kinase is thus not 

 appropriate in its strictest sense. 



An interesting feature of the deoxynucleotide kinases of E. coli is 

 that they are markedly influenced by bacteriophage infection. Activities 

 of dTMP and dGAlP kinases rapidly increase after T2, T4, or T6 infec- 

 tion, and dTMP, dGAIP, and dCMP kinases increase after T5 infection 

 (Kornberg et al., 1959; Bessman, 1959). In addition, a new kinase, un- 

 detectable in the uninfected cell, which catalyzes the phosphoiylation of 

 hydroxymethyldeoxycytidylate is formed after infection with T2, T4, 

 and T6 bacteriophages (Kornberg et al., 1959; Somerville et al., 1959). 

 Recently it has been shown that the dGMP and dTMP kinases formed 

 after bacteriophage infection are different from their counterparts in the 

 normal cell (Bessman and Van Bibber, 1959; Bello et al., 1961a, b). 

 They can be separated from the kinases of the uninfected cell by chroma- 

 tography on DEAE cellulose columns and have different properties. For 

 example, dGMP kinase from T2-infected E. coli is absolutely specific 

 for the deoxyribonucleotide. It will not phosphoiylate ribo-GMP, 

 whereas the enzyme from the uninfected cell will. 



Purification of dGMP kinase from T2-infected cells has led to a 

 concomitant purification of dTMP and 5-hydroxymethyldeoxycytidylate 

 kinases (Bessman and Bello, 1961). Since the ratios of the three activities 

 do not change over a 200-fold range in purification these authors investi- 

 gated the possibility that all three activities resided in the same protein. 

 Results of heat-inactivation studies and competitive inhibition measure- 

 ments have led to the tentative conclusion that the three kinases are 

 associated with one protein, although the data can be interpreted equally 

 well by assuming the activities are associated with three veiy closely 

 related proteins. Preliminaiy studies with the T5-induced kinases show 

 that the dCMP, dGMP, and dTMP kinases, which increase after infec- 

 tion, chromatograph in the same place on columns of DEAE cellulose, 

 suggesting a close relationship if not identity of these three activities. 

 Again, the phage-induced dCMP kinase differs from the dCMP kinase of 

 normal cells by requiring deoxyribonucleotides as substrates. Ribo-GMP 

 or CMP are not phosphoiylated. Thus, in this case and in the T2- 

 infected cell, the name "deoxyribonucleotide" kinase is truly applicable. 

 These are the only two members of the so-called deoxyribonucleotide 

 kinases which are specific for the deoxy compounds. 



B. DEOXYNUCLEOSIDE DIPHOSPHATE KINASES 



The phosphorylation of deoxyribonucleotides most likely proceeds 

 through the corresponding diphosphates to the triphosphate level. In the 



