Isolation of the regulatory segment of the biotin operons of Escherichia coli K-12.

A DNA fragment of 463 base pairs has been isolated by HpaII digestion of the EcoRI cleaved lambdabiot124-10 DNA fragment containing the Escherichia coli biotin gene cluster. This HpaII subfragment contains the biotin regulator region. The biotin regulator DNA has been characterized by electron microscopic heteroduplex analysis, RNA polymerase binding capacity, and the ability to initiate leftward and rightward transcriptions. The two RNA polymerase binding sites are located 63 base pairs and 117 base pairs away from the left end of the HpaII fragment. Both the left- and rightward RNA transcripts have adenosine triphosphates at their 5' end.