title: 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.
abstract: 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.
mesh_terms: D001665:Binding Sites; D004256:DNA Polymerase I / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000528:radiation effects; D004269:DNA, Bacterial / Q000096:biosynthesis*; D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D008239:Lysine; D010446:Peptide Fragments / Q000302:isolation & purification; D011732:Pyridoxal Phosphate / Q000494:pharmacology*; D014357:Trypsin; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D010446:Peptide Fragments; D011732:Pyridoxal Phosphate; D004256:DNA Polymerase I; D014357:Trypsin; D008239:Lysine