Structural characteristics of FCPI-1 (RedCAP).
(A) Interactions of FCPI-1 with PsaB, PsaI, and PsaL viewed from the stromal (left) and lumenal (right) sides. The areas encircled by black squares are enlarged in panels B, C. Yellow, PsaB; magenta, PsaI; dark red, PsaL; red, FCPI-1. (B, C) Protein-protein interactions of FCPI-1 with PsaL (B) and PsaB/PsaI/PsaL (C), respectively. Interactions are indicated by dashed lines, and the numbers are distances in Å. Amino acid residues participating in the interactions are labeled; for example, S139/1 means Ser139 of FCPI-1. B, PsaB; I, PsaI; L, PsaL; 1, FCPI-1. (D) Characteristic loop structure from Q96 to T116 in FCPI-1 viewed from the lumenal side. Q96 and T116 are labeled with sticks and the Q96–T116 loop is colored pink. (E) Superpositions of FCPI-1 (red) with FCPI-2 (green), FCPI-3 (blue), FCPI-4 (magenta), and FCPI-5 (orange). Only proteins are depicted. The Q96–T116 loop of FCPI-1 is colored pink and Q96 and T116 are labeled with sticks.