Enzymological Characterization of Human DNA Polymerases-α and β
During the past few years, we have described the results of an extensive series of investigations of the enzymological properties of essentially homogeneous preparations of human DNA polymerases-α and β1-3 that are devoid of contaminating or associated endo- or exodeoxyribonuclease activities4,5. These studies have demonstrated a number of striking differences between the two enzymes with respect to their ability to catalyze deoxynucleotide incorporation on a variety of defined, natural and synthetic DNA primer-templates4-8 and have suggested that there might be equally profound differences, possibly of physiological significance, in the nature of the specific molecular signals that regulate their catalytic interactions with nucleic acids. To pursue these observations in the face of exceedingly limited quantities of purified enzyme protein, we have successfully exploited the power of classical steady-state kinetics methodology to illuminate many of the key features of the polymerase-primer-template interaction and to gain substantial new insights into the fundamental mechanisms of polymerase catalysis. In performing these studies, we have employed direct sedimentation binding assays and novel methods of analysis of polymerase products synthesized on DNA molecules of known sequence to obtain, in every instance, direct physical corroboration of the principal conclusions derived from the kinetics experiments. We have thus been able to provide important reassurance of the validity of the kinetics interpretations and obviate much of the concern that might appropriately arise from the indirect nature of kinetics analyses, particularly in complex systems.
KeywordsDivalent Cation American Chemical Society Inhibitory Potency Dixon Plot Template Length
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