This family consists of several bacterial replication initiation and membrane attachment (DnaB) proteins, as well as DnaD which is a component of the PriA primosome. The PriA primosome functions to recruit the replication fork helicase onto the DNA [2]. The DnaB protein is essential for both replication initiation and membrane attachment of the origin region of the chromosome and plasmid pUB110 in Bacillus subtilis. It is known that there are two different classes (DnaBI and DnaBII) in the DnaB mutants; DnaBI is essential for both chromosome and pUB110 replication, whereas DnaBII is necessary only for chromosome replication [1]. DnaD has been merged into this family. This family also includes Ftn6, a cyanobacterial-specific divisome component possibly playing a role at the interface between DNA replication and cell division [3]. Ftn6 possesses a conserved domain localised within the N-terminus of the proteins. This domain, named FND, exhibits sequence and structure similarities with the DnaD-like domains Pfam:PF04271 now merged into Pfam:PF07261.

1: Nucleotide sequence of Bacillus subtilis dnaB: a gene essential for DNA replication initiation and membrane attachment. Hoshino T, McKenzie T, Schmidt S, Tanaka T, Sueoka N; Proc Natl Acad Sci U S A 1987;84:653-657. PMID:3027697

2: DnaB, DnaD and DnaI proteins are components of the Bacillus subtilis replication restart primosome. Bruand C, Farache M, McGovern S, Ehrlich SD, Polard P; Mol Microbiol 2001;42:245-255. PMID:11679082

3: The cyanobacterial cell division factor Ftn6 contains an N-terminal DnaD-like domain. Marbouty M, Saguez C, Chauvat F; BMC Struct Biol. 2009;9:54. PMID:19698108