Molecular organization and nucleotide sequence of the recG locus of Escherichia coli K-12

Abstract

The nucleotide sequence of the Escherichia coli K-12 recG gene was determined. recG was identified as an open reading frame located between the spoT operon and the convergent gltS gene. It encodes a polypeptide of 693 amino acids which was identified as a 76-kDa protein by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after it was labeled with [35S]methionine in maxicells. The sequence determined revealed no obvious promoter. Synthesis of RecG by plasmids carrying the intact gene varied with the orientation of the insert relative to the vector promoter and with the extent of upstream spoT operon sequence included in the construction. It is concluded that recG is the fourth and last gene in the spoT operon, although a possible promoter for independent transcription of spoU and recG was identified near the end of the spoT gene. The primary sequence of RecG revealed that it is related to proteins that act as helicases and has a well-conserved motif identified with ATP binding.