Expression and Regulation of the yggG Gene of Escherichia coli

Our previous study indicated that Era, a membrane-associated GTPase essential for the survival of Escherichia coli, binds with the product of the yggG gene. However, the expression, regulation, and function of the yggG gene have not been established. In this study, the transcript of the yggG gene was determined by analysis of the 5′-end of the yggG mRNA using 5′-RACE (5′-rapid amplification of cDNA ends) method. The promoter and transcription regulatory regions of yggG were analyzed through systematic analysis of the transcriptional activity of the fragment containing a 339-bp 5′ flanking sequence of yggG mRNA. The results showed that the sequence −39/−1 upstream of the transcriptional start site of the yggG gene contained a core promoter required for the expression of 25-kDa YggG protein, whereas the −106/−40 region was associated with transcriptional upregulation of yggG under heat shock. Immunocytochemistry and subcellular fraction analysis showed that YggG was a membrane-associated protein. Based on these results, we confirmed that the −39/780 region contains the whole set of the promoter and coding sequence of the yggG gene. The expression regulation of the yggG gene under stress conditions and the YggG protein located on cell membrane are consistent with the bioinformatics analysis that YggG, a metallopeptidase, is functional as a heat shock protein that is associated with Era functions.