Enzymology
Kinetic and Structural Impact of Metal Ions and Genetic Variations on Human DNA Polymerase ι
DNA polymerase (pol) ι is a Y-family polymerase involved in translesion synthesis, exhibiting higher catalytic activity with Mn2+ than Mg2+. The human germline R96G variant impairs both Mn2+-dependent and Mg2+-dependent activities of pol ι, whereas the Δ1–25 variant selectively enhances its Mg2+-dependent activity. We analyzed pre-steady-state kinetic and structural effects of these two metal ions and genetic variations on pol ι using pol ι core (residues 1–445) proteins. The presence of Mn2+ (0.15 mm) instead of Mg2+ (2 mm) caused a 770-fold increase in efficiency (kpol/Kd,dCTP) of pol ι for dCTP insertion opposite G, mainly due to a 450-fold decrease in Kd,dCTP.Roles of Residues Arg-61 and Gln-38 of Human DNA Polymerase η in Bypass of Deoxyguanosine and 7,8-Dihydro-8-oxo-2′-deoxyguanosine
Background: Arg-61 and Gln-38 of human DNA polymerase (hpol) η play important roles in the catalytic reaction.Results: Mutations R61M or Q38A/R61A dramatically disrupt the activity of hpol η.Conclusion: Polarized water molecules can mimic and partially compensate for the missing side chains of Arg-61 and Gln-38 in the Q38A/R61A mutant.Significance: The positioning and positive charge of Arg-61 synergistically contribute to the activity of hpol η, with additional effects of Gln-38.
