Fig. 4: Identifying important residues for self/nonself-discrimination between similar eSRK–SP11 pairs.

a Model structure of S₄₆-eSRK–S₄₆-SP11 complex. Green and cyan represent two S₄₆-SP11 molecules in the heterotetramer, and pink and yellow represent two S₄₆-eSRK molecules. Residues mutated in the pull-down assay are shown in orange. Left and right panels show close-up views of interfaces around CR III and around CR I–II, respectively. a, c Subscripts to the right of residue numbers indicate chain ID in the complex (a, b, eSRK; c, d, SP11). b Pull-down of S₈-meSRK-HLH and its derivatives with biotin-S₈-SP11 was performed as in Fig. 1b. S₈-meSRK-HLH^{N271S,E273D,N337I} and S₈-meSRK-HLH^{N271S,E273D,N337I,E80G,S190P,Y198F,R367T} proteins lost the ability to bind S₈-SP11. c Model structure of the S₃₆-eSRK–S₃₆-SP11 complex. An overview of S₃₆-SP11 docked with S₃₆-eSRK dimer is shown in the left panel. Cyan represents S₃₆-SP11 molecule, and pink and yellow represent two S₃₆-eSRK molecules. Residues mutated in the bioassay are shown in orange. A close-up view of the CR III of S₃₆-SP11 is shown in the right panel. The H62R mutation is shown in pink. Distances are shown in angstroms. d Pollination bioassay. S₃₆-SP11- or mutant-treated (50 pmol) S₃₆S₃₆ pistils were pollinated with S₁₂ pollen grains. Pollen tubes were observed by UV fluorescence microscopy after aniline blue staining. Arrow shows pollen tubes. Scale bars, 100 μm.