Rate of Translation and Kinetics of Processing of Newly Synthesized Molecules of Two Major Outer‐Membrane Proteins, the OmpA and OmpF Proteins, of Escherichia coli K12

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Abstract
The rate of synthesis of the OmpA and OmpF proteins, 2 of the major outer membrane proteins of E. coli K12, was determined. At 25.degree. C both proteins were translated at 6.5 amino acids/s, and the OmpF protein was translated at 15 amino acids at 37.degree. C. The former rate corresponded to a synthesis time of just over 50 s for both proteins, which is significantly faster than their reported rates of assembly into the outer membrane at 25.degree. C. The kinetics of processing of the pro-OmpF protein were also investigated in detail, and the pro-OmpF half-life estimated to be 3-5 s at 25.degree. C. A fraction of the precursor was processed more slowly, which may explain the discrepancy between these data and an earlier published estimate of 30 s. Pro-OmpA protein was processed with similar kinetics. The rate-limiting step in the assembly of both proteins into the outer membrane is post-translational and follows the processing step.