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Biochemistry. 1988 Sep 6;27(18):6710-6.

Pyridoxal 5'-phosphate mediated inactivation of Escherichia coli DNA polymerase I: identification of lysine-635 as an essential residue for the processive mode of DNA synthesis.

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Department of Biochemistry, University of Medicine and Dentistry, New Jersey Medical School, Newark 07103-2757.


Inactivation of Escherichia coli DNA polymerase I by pyridoxal 5'-phosphate treatment results from its reactivity at multiple lysine residues. One of these residues, lysine-758, has been shown to be located at the substrate binding site in DNA polymerase I [Basu, A., & Modak, M. J. (1987) Biochemistry 26, 1704-1709]. We now demonstrate that lysine-635 is another important target of pyridoxylation; modification of this site results in decreased rates of DNA synthesis. Addition of template-primer with or without substrate deoxynucleoside triphosphate protects lysine-635 from pyridoxylation. Analysis of the initiation versus elongation phase of DNA synthesis by lysine-635-modified enzyme revealed that elongation of the DNA chain is severely affected by the lysine-635 modification. We therefore conclude that this lysine residue plays an important role in the processive mode of DNA synthesis by E. coli DNA polymerase I.

[Indexed for MEDLINE]

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