Crystal structure of DNA polymerase I from Thermus phage G20c

This study describes the structure of DNA polymerase I from Thermus phage G20c, termed PolI_G20c. This is the first structure of a DNA polymerase originating from a group of related thermophilic bacteriophages infecting Thermus thermophilus, including phages G20c, TSP4, P74-26, P23-45 and phiFA and the novel phage Tth15-6. Sequence and structural analysis of PolI_G20c revealed a 3 ′ – 5 ′ exonuclease domain and a DNA polymerase domain, and activity screening confirmed that both domains were functional. No functional 5 ′ – 3 ′ exonuclease domain was present. Structural analysis also revealed a novel specific structure motif, here termed S β α R, that was not previously identified in any polymerase belonging to the DNA polymerases I (or the DNA polymerase A family). The S β α R motif did not show any homology to the sequences or structures of known DNA polymerases. The exception was the sequence conservation of the residues in this motif in putative DNA polymerases encoded in the genomes of a group of thermophilic phages related to Thermus phage G20c. The structure of PolI_G20c was determined with the aid of another structure that was determined in parallel and was used as a model for molecular replacement. This other structure was of a 3 ′ – 5 ′ exonuclease termed ExnV1. The cloned and expressed gene encoding ExnV1 was isolated from a thermophilic virus metagenome that was collected from several hot springs in Iceland. The structure of ExnV1, which contai...
Source: Acta Crystallographica Section D - Category: Biochemistry Authors: Tags: DNA polymerase I Thermus phage G20c Thermus thermophilus thermophilic bacteriophages structural motifs PolI_G20c research papers Source Type: research