Comparison of the signature motif, scaffolding domain, pin motif/N-terminal region, and protomer interfaces for H. sapiens, S. rosetta, and S. purpuratus caveolins. (A–I) Detailed view of the signature motifs (A–C) (blue), scaffolding domains (D–F) (green), and pin motif (G) (red) or N-terminal variable regions (H and I) (yellow) of the human Cav1, S. rosetta caveolin, and S. purpuratus caveolin complexes. One protomer is colored according to the structural elements as described in Fig. 2, while other protomers of the complex are depicted in transparent gray. The first and last residues of the motifs are labeled, and any residues that are absolutely conserved between the three caveolins are labeled and marked with an asterisk. (J–L) Overall structure of caveolin complexes highlighting one protomer, i, in light blue and its interacting protomers in magenta. The interacting protomers are labeled i −2 to i + 2 for the caveolin complexes with the S. rosetta caveolin complex also exhibiting interactions at protomers i −5 and i + 5. (M–O) Packing of two protomers with secondary structure elements labeled. (P–R) Zoomed-in view of membrane-facing residues indicated by a dashed box on overall caveolin structures in J–L. Complexes are rotated −160° around the x axis from J–L to show the membrane-facing surface. Membrane-interacting residues of interest are noted. (S–U) Cartoon depiction of caveolin complexes to illustrate the organization of interacting protomers. Color and labeling scheme remain the same as (J–L).