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![[Figure 4]](ji5027fig4mag.jpg)
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Figure 4
The electron density of galactose and sucrose products at the active site and sequence alignment of the loop region. (a) Both the galactose and sucrose products (yellow sticks) are clearly revealed with electron densities (gray mesh) at the −1 subsite and the secondary product-binding site, respectively, after co-crystallization of D383A and raffinose for two months. The secondary product-binding site is near the surface of the catalytic binding cavity, which is formed in part by a unique loop with three short helices (magenta) and a β-turn (residues 75–78). (b) The interaction network with distances between galactose, sucrose (yellow sticks) and residues (green and magenta sticks) is shown. Water molecules are presented as cyan spheres. (c) A sequence alignment shows that the loop region (residues 329–352 in the green box) exists exclusively in AtAkαGal3 and possibly in the RFO synthase family from different plants, including rice (ABF99470; Rice_seed_imbibition), soybean (XP_006576826; Raf_Soybean), pea (RFS_PEA; Raf_Pea), jute (OMO49898; Raf_Corchorus), cucumber (AAD02832; Raf_Cucumis), cacao (EOY02480; Raf_Cacao), japonica rice (XP_015621501; Raf_Oryza sativa), melon (NP_001284472; Raf_II_Melon), yoshino cherry (PQQ02596; STA_Prunus), clementine (XP_006444535; STA_Citrus) and Arabidopsis (NP_192106; STA_A. thaliana). Residue numbers are based on AtAkαGal3. |
![[Figure 4]](ji5027fig4.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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