Transcriptional control in the L-arabinose operon of Escherichia coli B-r.

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 lambdah80dara 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.