DNA Polymerases of Low-GC Gram-Positive Eubacteria: Identification of the Replication-Specific Enzyme Encoded by dnaE

Abstract

ABSTRACT dna E, the gene encoding one of the two replication-specific DNA polymerases (Pols) of low-GC-content gram-positive bacteria (E. Dervyn et al., Science 294:1716-1719, 2001; R. Inoue et al., Mol. Genet. Genomics 266:564-571, 2001), was cloned from Bacillus subtilis , a model low-GC gram-positive organism. The gene was overexpressed in Escherichia coli . The purified recombinant product displayed inhibitor responses and physical, catalytic, and antigenic properties indistinguishable from those of the low-GC gram-positive-organism-specific enzyme previously named DNA Pol II after the polB -encoded DNA Pol II of E. coli . Whereas a polB -like gene is absent from low-GC gram-positive genomes and whereas the low-GC gram-positive DNA Pol II strongly conserves a dnaE -like, Pol III primary structure, it is proposed that it be renamed DNA polymerase III E (Pol III E) to accurately reflect its replicative function and its origin from dnaE . It is also proposed that DNA Pol III, the other replication-specific Pol of low-GC gram-positive organisms, be renamed DNA polymerase III C (Pol III C) to denote its origin from polC . By this revised nomenclature, the DNA Pols that are expressed constitutively in low-GC gram-positive bacteria would include DNA Pol I, the dispensable repair enzyme encoded by polA , and the two essential, replication-specific enzymes Pol III C and Pol III E, encoded, respectively, by polC and dnaE .