Pre-steady-state kinetic characterization of the DinB homologue DNA polymerase of Sulfolobus solfataricus

Janina Cramer, Tobias Restle*

*Corresponding author for this work
18 Citations (Scopus)


Equilibrium as well as pre-steady-state measurements were performed to characterize the molecular basis of DNA binding and nucleotide incorporation by the thermostable archaeal DinB homologue (Dbh) DNA polymerase of Sulfolobus solfataricus. Equilibrium titrations show a DNA binding affinity of about 60 nM, which is ∼ 10-fold lower compared with other DNA polymerases. Investigations of the binding kinetics applying stopped-flow and pressure jump techniques confirm this weak binding affinity. Furthermore, these measurements suggest that the DNA binding occurs in a single step, diffusion-controlled manner. Single-turnover, single dNTP incorporation studies reveal maximal pre-steady-state burst rates of 0.64, 2.5, 3.7, and 5.6 s-1 for dTTP, dATP, dGTP, and dCTP (at 25 °C), which is 10-100-fold slower than the corresponding rates of classical DNA polymerases. Another unique feature of the Dbh is the very low nucleotide binding affinity (Kd ∼ 600 μM), which again is 10-20-fold lower compared with classical DNA polymerases as well as other Y-family polymerases. Surprisingly, the rate-limiting step of nucleotide incorporation (correct and incorrect) is the chemical step (phosphoryl transfer) and not a conformational change of the enzyme. Thus, unlike replicative polymerases, an "induced fit" mechanism to select and incorporate nucleotides during DNA polymerization could not be detected for Dbh.

Original languageEnglish
JournalJournal of Biological Chemistry
Issue number49
Pages (from-to)40552-40558
Number of pages7
Publication statusPublished - 09.12.2005


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