FIGURE 4.
Targeted disulfide cross-linking between FliN and FliMC. A, cross-linking by the relatively high-yield Cys pairs N86/M316 and N134/M310 catalyzed by copper-phenanthroline (Cu-phen). B, cross-linking of the N86/M316 and N134/M310 pairs by oxidation with iodine. C, single-Cys controls demonstrating the requirement for Cys residues in both proteins. D, shift in mobility of the FliM-FliN heterodimer when a His tag is introduced in FliN. The cross-linking used copper-phenanthroline. E, cross-linking involving additional Cys pairs. Results with copper-phenanthroline are shown; with iodine, FliM-FliN cross-linking was observed reproducibly, but yields were lower (not shown). w.t., wild-type.