Figure 3.

X-ray crystal structure of the rice CesA8 P-CR (Ala-399 to Gln-475). A, Ribbon model of the P-CR crystal structure (green) encased in an electron density omit map (2σ; gray mesh). Colored boxes and rotation arrows depict areas inset in C (yellow) and D (purple), respectively. The red arrow (A and B) points to the bend in HX1 between Arg-414 and Pro-418. B, Details of the interactions between HX1 and HX2, showing R groups and highlighting knob-in-hole interactions. In this orientation, Arg-414 and the stacked Arg-454 and Arg-458 are exterior facing functionalities; Arg-454 (orange) is mutated to Lys in the cellulose-deficient fra6 mutant (Zhong et al., 2003). C, Structure of the P-CR LP region, highlighted in the yellow box in A and rotated 90° relative to A to highlight loop structures. D, Structure of the upper region of the P-CR hydrophobic core, highlighted in the purple box in A and rotated 90° relative to A to highlight the hydrophobic core. Aromatic residues from HX1, HX2, and the LP are tightly packed, forcing Trp-432 to become solvent exposed.