Fig. 3: Putative transmembrane helices of SGS1.

a Transparent map density of SGS1 (left panel) and the surface slice (right panel) showing daisy-chained helices predicted to form transmembrane helices. The flexible, unmodeled regions are indicated with dashed lines. b Close-up view of the daisy-chained helices engaged in hydrophobic patches. c Prediction of transmembrane helices in SGS1 using CCTOP server⁵⁶. The confident score was hit rate considering all the prediction methods. The unmodeled regions are indicated as dashed lines and dashed rectangles. d Comparison of the surface opening/gate in SGS1, Tc toxin and teneurin. These three structures are aligned based on their Rhs/YD shell and displayed separately. e Multiple sequence alignment of the C-terminal moieties in mosquito SGS proteins. Two layers of secondary structure are shown. The upper layer represents the prediction result shown in (c); the lower layer is derived from our cryo-EM structure. The putative furin cleavage sites are colored with transparent yellow. f The putative furin cleavage sites are aligned and indicated using residue numbers at their P1 position (the cleavage occurs right after P1).