FIGURE 1.

RXLR effectors AVR3a11 and PexRD2 adopt a structurally conserved but adaptable fold. a, oomycete RXLR effectors are modular proteins comprising a secretion signal (cyan), RXLR translocation motif (purple), and an effector domain (green). b, structural alignment and secondary structure elements of the effector domains of AVR3a11 and PexRD2. W-motifs (cyan) and Y-motifs (lilac) are colored, with key residues (as discussed under “Results and Discussion”) boxed. c, the structure of AVR3a11 is a monomeric four-helix bundle with a hydrophobic core. Carbon atoms of key residues in the W- and Y-motifs are colored as boxed in b; loop-3 is shown in purple. d, PexRD2 is a dimer with a hydrophobic interface, including residues Val⁷³, Asp⁷⁴, Ala⁷⁷, Thr⁸³, Ile⁸⁶, Ala⁹⁰, Met⁹⁶, Gly¹⁰⁰, Met¹⁰⁵, Leu¹⁰⁸, Leu¹⁰⁹, and Leu¹¹² (shown for one monomer only). α-Helices are labeled to correspond to equivalent positions in AVR3a11. e, the AVR3a11/PexRD2-monomer overlay generated using SSM, showing the conserved fold. Protein structures are colored as in c and d with key residues of the W- and Y-motifs colored as in b.