Figure 1.

Sequences, topologies, and modeled structures of the 15 proteins used in this study. (A) The repeating TPR motif sequences used (each repeat contains two α-helices) are as follows: CTPRn (red), CTPR-YD (gray), and CTPR-YD-loop (green). (B) The topology of the CTPR series of four proteins containing only the “CTPR” motif (CTPR2, CTPR3, CTPR4, and CTPR6) (9) is shown. Repeats are colored as per (A) to show that all proteins in this series contain only the CTPR sequence. (C) The topology of the CTPR series containing “CTPR,” “CTPR-Y91D,” and “CTPR-Y91D-loop” motifs (CTPR3-YD, CTPR6-YD, CTPR6-YD-loop10, CTPR6-YD-loop15, etc.) is shown. Repeats are colored as per (A) to show where the loop-containing and YD-containing repeats occur. (D) The topology of the CTPR2 series containing “CTPRn,” “CTPR-Y91D,” and “CTPR-Y91D-loop” motifs (CTPRa2 and CTPR2 with either a 10-residue or a 25-residue loop between the two repeats and a version of them with the Y-to-D point mutation) is shown. Repeats are colored as per (A) to show where the loop-containing and YD-containing repeats occur. (E) A ribbon representation of the atomic structures of CTPR2, CTPR3, and CTPR6 based on the crystal structure 2HYI (56) is shown. The dots represent the fact that this series also includes CTPR4 (data not shown). Repeats are colored as per (A) to show that all proteins contain only the CTPRn sequence. (F) A ribbon representation of the atomic structures of CTPR3-YD, CTPR6-YD, and CTPR6-YD-loop proteins based on crystal structure 2HYI (56) is shown. Repeats are colored as per (A) to show that, for example, CTPR3-YD is composed of two CTPR repeats and a C-terminal CTPR-YD repeat. In the representation of the CTPR6-YD-loop proteins, the CTPR-YD-loop motif is located in repeat 3 (green). The loops were inserted after the third repeat (green) and before the fourth repeat (red). The sequences for all proteins are found in Table S1. To see this figure in color, go online.