T4 polynucleotide kinase; cloning of the gene (pseT) and amplification of its product.

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Abstract
The T4 gene (pseT) for polynucleotide kinase (pnk) has been cloned in lambda. Induction of a lambda E‐W‐S‐cI857 prophage in which the pseT gene can be transcribed from the late lambda promoter, PR1, leads to greater than 100‐fold amplification of pnk activity; pnk comprises approximately 7% of the total soluble cell protein. The purified enzyme, as expected, is both a 5′‐kinase and a 3′‐phosphatase. The amino acid sequence deduced from an open reading frame identified as the pseT gene contains a sequence which corresponds particularly well with that part of the adenine nucleotide binding site of adenylate kinase shown to form a flexible loop. A deletion mutant that lacks 5′‐kinase activity, and possibly also 3′‐phosphatase activity, has lost two amino acids from within the proposed loop structure. A second region of the pnk sequence shares homology with phosphoglycerate kinase, yeast inorganic pyrophosphatase and histone 2b from various organisms.