Pulse-chase assays with TatA TMH length mutants.A, SufI transport activity supported by TatA addition and deletion mutants (ACa1–4 and Ad1–3), as monitored by pulse-chase experiments. Autoradiograms developed from 8 to 16% acrylamide gels are shown; gels are representative of at least two biological replicates. B and C, quantitation of the gels in A. The ordinate represents the ratio of intensities of the mature bands divided by the intensities of the mature + precursor bands. Data were fitted to a rising exponential model, and the corresponding initial velocity (V0) is shown in (D). m, mature SufI; p, precursor; TMH, transmembrane alpha helix.