FIGURE 7.
Comparison of the structures of the peptide pheromones. A, structures of ESP1 (left), attractin (PDB code 1T50) (middle), and Er-1 (PDB code 2ERL) (right) are shown as green, magenta, and cyan ribbon representations, respectively. Each helix is labeled as H1, H2, or H3. The N- and C termini are marked with N and C, respectively. Disulfide bridges are depicted by yellow balls and sticks. The view of the structures in the lower panel is a 90° rotation of the view of the structures in the upper panel around the horizontal axis. Although the H3 helix of attractin is described as a short α-helix in the PDB, this was not mentioned in published reports (33). B, structures of mammalian peptide pheromones with β-barrel topology. Structures of MUP (PDB code 1MUP) (left), α2u-globulin (PDB code 2A2U, chain A) (middle), and aphrodisin (PDB code 1E5P, chain A) (right), are shown as blue, beige, and orange ribbon representations, respectively. The N and C termini and the disulfide bridges are depicted with the same color scheme used in A.