FIGURE 5.

Secondary structure predictions. A, sequence alignments of the segments corresponding to γSer²¹⁴–Glu²⁶¹ of mENaC. The alignments of γ subunits of mouse, rat, and human ENaCs were performed with Vector NTI 11.0 (Invitrogen), and only the regions of interest are shown. The full-length identities at the amino acid level are 97% between γmENaC and γrENaC and 86% between γmENaC or γrENaC and γhENaC. γHis²³⁹ is identified by an asterisk. B, secondary structure predictions of the mutated region of γmENaC. The predictions were performed with Network Protein Sequence Analysis (38). h, helical; e, extended; t, turn; and c, coiled. C and D, helical wheel projections. The helical wheels were generated with Membrane Protein Explorer (version 3.1) (39). Residues where mutations resulted in significant reductions or enhancements of Na⁺ self-inhibition, compared with WT, are identified by downward arrows and upward arrows, respectively. Gray spheres denote the residues where Cys substitutions led to significant changes in currents following MTSET application. A dashed line separates the two faces with distinct changes on the projected helical wheel. E, sequence alignments of the segments corresponding to the 22-residues tracts within γmENaC (γPhe²²⁵–γGln²⁴⁶), αmENaC, and βmENaC.