This is the first N-terminal domain, NI domain, of the DNA polymerase III polC subunit A that is found only in Firmicutes. DNA polymerase polC-type III enzyme functions as the 'replicase' in low G + C Gram-positive bacteria [1]. Purine asymmetry is a characteristic of organisms with a heterodimeric DNA polymerase III alpha-subunit constituted by polC which probably plays a direct role in the maintenance of strand-biased gene distribution; since, among prokaryotic genomes, the distribution of genes on the leading and lagging strands of the replication fork is known to be biased [2]. It has been predicted that the N-terminus of polC folds into two globular domains, NI and NII. A predicted patch of elecrostatic potential at the surface of this domain suggests a possible involvement in nucleic acid binding [3]. This domain is associated with DNA_pol3_alpha Pfam:PF07733 and DNA_pol3_a_NI Pfam:PF11490.

1: A 'gram-negative-type' DNA polymerase III is essential for replication of the linear chromosome of Streptomyces coelicolor A3(2). Flett F, de Mello Jungmann-Campello D, Mersinias V, Koh SL, Godden R, Smith CP; Mol Microbiol. 1999;31:949-958. PMID:10048037

2: Replication-associated purine asymmetry may contribute to strand-biased gene distribution. Hu J, Zhao X, Yu J; Genomics. 2007;90:186-194. PMID:17532183

3: The N-terminal region of the bacterial DNA polymerase PolC features a pair of domains, both distantly related to domain V of the DNA polymerase III tau subunit. Timinskas K, Venclovas C; FEBS J. 2011;278:3109-3118. PMID:21740522