Nucleotide sequence of dnaB and the primary structure of the dnaB protein from Escherichia coli

Abstract

We have determined the nucleotide sequence of the dnaB gene and the primary structure of the dnaB protein of Escherichia coli (Arai, K., Yasuda, S., and Kornberg, A. (1981) J. Biol. Chem. 256, 5247-5252). The coding region for the dnaB protein is 1413 base pairs followed by double stop codons and preceded by a possible promoter sequence. The dnaB gene lacks a typical Shine-Dalgarno sequence. The primary structure deduced from the DNA sequence is consistent with the protein chemical data. The dnaB protein contains 470 amino acid residues and has a calculated molecular weight of 52,265. In the mature protein, the initiator methionine residue is removed in vivo leaving alanine as the NH2-terminal residue. Based on the amino acid sequence, we predict that the dnaB protein may be composed of two domains. A hydrophilic NH2-terminal region (residues 1-20) is followed by a compact domain and a possible hinge region (residues 21-172) consisting primarily of alpha-helix. The sites of facile tryptic cleavage are at the arginine residues at 14 and 171. The DNA-dependent ATPase domain (residues 172-470) is located at the COOH-terminal end of the protein.