Extended Data Figure 5. Filament formation inhibits hRegIIIα membrane toxicity.

Here we examined the functional properties of the hRegIIIα VH mutant carrying a mutation near the C-terminus [C-terminal sequence: FTD (wild-type)→VH(mutant)], thus truncating the protein near the C-terminus. The VH mutant lacks the ability to form filaments but retains the ability to form pores. In accordance with its pore-forming activity, the hRegIIIα VH mutant retained membrane toxicity against liposomes and live bacteria. In fact, membrane toxicity was modestly enhanced in the hRegIIIα VH mutant, suggesting that trapping of the pore complexes in filaments inhibits their membrane permeabilizing activity. This function contrasts with that of human α-defensin-6 filaments, which directly trap bacteria in “nanonets”²².

a, 1.0 μM wild-type (wt) and hRegIIIα (VH) mutant was added to 10 μM CF-loaded liposomes and dye release was monitored. The detergent octylglucoside (OG) was added at the end of the experiment to disrupt remaining liposomes. b, Initial rate of liposome dye release (10 μM lipid) as a function of wild-type and mutant hRegIIIα concentration. c, 5.0 μM wild-type or hRegIIIα (VH) mutant was assayed for membrane disruptive activity toward whole bacteria using the SYTOX uptake assay described in Fig. 1. Assays were performed in triplicate. Error bars, ±SD; ***, p<0.001.