Replication of duplex DNA by bacteriophage T7 DNA polymerase and gene 4 protein is accompanied by hydrolysis of nucleoside 5'-triphosphates.

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Abstract
Homogeneous preparations of phage T7 gene 4 protein catalyze the hydrolysis of dNTP [deoxyribonucleoside triphosphates] and rNTP [ribonucleoside triphosphates] to NDP [nucleoside diphosphates] and Pi in the presence of single-stranded DNA. Synthesis on single-stranded DNA by T7 DNA polymerase (DNA nucleotidyltransferase; deoxynucleosidetriphosphate:DNA deoxynucleotidyltransferase, EC 2.7.7.7) does not affect the hydrolysis of NTP by the gene 4 protein. Gene 4 protein does not catalyze the hydrolysis of NTP in the presence of duplex DNA, nor can T7 DNA polymerase use duplex DNA as a template. The 2 proteins together can replicate duplex DNA, and under these conditions, synthesis is accompanied by hydrolysis of NTP. During synthesis on duplex templates in the presence of T7 DNA polymerase, gene 4 protein, dNTP and rNTP, 4.2 NTP are hydrolyzed for each dNMP polymerized. 2''3''-Dideoxy-TTP, an inhibitor of DNA synthesis, inhibits hydrolysis by the gene 4 protein during synthesis on duplex DNA, and .beta.,.gamma.-methylene-dTTP, an inhibitor of hydrolysis by the gene 4 protein, stops DNA synthesis on duplex DNA. The multiple activities of gene 4 protein reside in a single protein molecule.