Sequence of the regulatory region of omp T, the gene specifying major outer membrane protein a (3b) of Escherichia coli K-12: implications for regulation and processing.

The DNA of the promoter region of omp T, including the putative start for the pro-Omp T protein (pro-protein a), has been sequenced. Previous studies showed that trypsin inhibitors prevent the processing of pro-Omp T to Omp T protein which led to the prediction that the processing site would be a lysine or an arginine. The deduced amino acid sequence contains a lysine at amino acid 12 and an arginine at amino acid 17 from the N terminus. Chou-Fassman analysis would predict processing at the lysine (but not the arginine) to remove a 1389 dalton peptide, consistent with the fact that the estimated molecular masses of pro-Omp T and Omp T are 42 kd and 40 kd respectively. In addition, the predicted mRNA of the promoter region can form a stable secondary structure (-17.1 kcal) that sequesters the Shine-Dalgarno (SD) sequence as well as the initiator AUG codon. There is evidence that the per A (tpo, envZ) gene product is required for synthesis of Omp T protein (as well as several outer membrane and periplasmic proteins). The perA gene product could be activating translation of Omp T protein by disrupting the mRNA secondary structure that sequesters the SD sequence. Omp T protein synthesis is reduced at temperatures below 32 degrees C and this may also be related to the greater stability of the sequestered SD sequence of the mRNA at low temperature.