Fig. 5.

Reclosure of the gp16 stopper after DNA ejection. Wild-type SPP1 and phages with gp16 cysteine mutations were reduced (red.) with DTT and challenged or not (controls) with YueB780 to trigger DNA ejection (DNA rel.) followed, or not, by oxidation (oxid.) with DTNB. A final step of reduction with DTT (red.) was carried out, or not, to control that intersubunit cross-links were caused by disulfide bridges that are sensitive to reduction. The complete experimental procedure is detailed in Materials and Methods. Gp16 forms with n cross-linked subunits are labeled on the left of the Western blots.