The yigPP4P2 is the smallest known functional fragment of yigP gene in Escherichia coli.
We cloned the yigPP4P2 fragment into vector without exogenous promoter.
After transferring the new plasmid into JDP14, a yigP gene defect Escherichia coli strain, the normal growth of Escherichia coli was observed. This observation showed that the plasmid played a similar role of the temperaturesensitive plasmid suggesting the plasmid contained intact transcriptional unit. We further verified the transcription products from sequence of this plasmid by RTPCR, suggesting independent ability of transcription. We cloned a series of sub yigPP4P2 fragments with various lengths into promoter probe plasmid pSPZ for blue white screening and βgalactosidase enzyme activity assay. The results showed that pP40V3Z/JM83 and pP40V4Z/JM83 were positive (blue) and βgalactosidase enzyme activity were detected among them as well. Based on these observations, we concluded the promoter of Escherichia coli yigP is located upstream of the yigPP4P2 fragment; and the downstream boundary is located in sequence complementary to primer V4