Transcriptional Control in the l -Arabinose Operon of Escherichia coli B/r

Abstract

The structural genes involved in l -arabinose metabolism are regulated by the protein product of the araC gene. This protein functions as both an activator and repressor of enzyme synthesis in this gene complex. Using λ h80dara deoxyribonucleic acid in hybridization studies, we have shown that the ara operon, including structural genes araB, araA , and araD , is transcribed in the direction araB to araD and that initiation of transcription of these genes requires an active araC gene. The half-life of this message, approximately 3 min at 30 C, is the same in the presence or absence of the araC protein in the activator state. However, an unexplained 2-min lag in decay of ara messenger ribonucleic acid that does not occur in decay of lac messenger ribonucleic acid is observed. This lag period requires activated araC protein.