Structural features of hV3. (A) Cartoon representation of hV3 β-barrel scaffold, highlighting the distribution of cysteines. IMS, intermembrane space. (B) List of hV3 cysteine mutants used in this study. C→A substitutions are highlighted. (C) The secondary structure of hV3 mutants derived from far-UV CD. All the proteins exhibit a typical β-sheet structure. (D) Comparison of secondary structure content at ME₂₁₅ of the various cysteine mutants. Data for WT hV3 is shown as a shaded zone across the plot for comparison. Note how the mutation of C8 and C122 considerably lowers hV3 secondary structure (single Cys mutants C8A, C122A; and double mutants C2,8A, C2,122A, and C8,122A).