Engineered split in Pfu DNA polymerase fingers domain improves incorporation of nucleotide γ-phosphate derivative

Using compartmentalized self-replication (CSR), we evolved a version of Pyrococcus furiosus (Pfu) DNA polymerase that tolerates modification of the gamma-phosphate of an incoming nucleotide. A Q484R mutation in alpha-helix P of the fingers domain, coupled with an unintended translational termination-reinitiation (split) near the finger tip, dramatically improve incorporation of a bulky gamma-phosphate-O-linker-dabcyl substituent. Whether synthesized by coupled translation from a bicistronic (-1 frameshift) clone, or reconstituted from separately expressed and purified fragments, split Pfu mutant behaves identically to wild-type DNA polymerase with respect to chromatographic behavior, steady-state kinetic parameters (for dCTP), and PCR performance. Although naturally-occurring splits have been identified previously in the finger tip region of T4 gp43 variants, this is the first time a split (in combination with a point mutation) has been shown to broaden substrate utilization. Moreover, this latest example of a split hyperthermophilic archaeal DNA polymerase further illustrates the modular nature of the Family B DNA polymerase structure.