Ipomoelin, a Jacalin-Related Lectin with a Compact Tetrameric Association and Versatile Carbohydrate Binding Properties Regulated by Its N Terminus

Abstract

Many proteins are induced in the plant defense response to biotic stress or mechanical wounding. One group is lectins. Ipomoelin (IPO) is one of the wound-inducible proteins of sweet potato (Ipomoea batatas cv. Tainung 57) and is a Jacalin-related lectin (JRL). In this study, we resolved the crystal structures of IPO in its apo form and in complex with carbohydrates such as methyl α-D-mannopyranoside (Me-Man), methyl α-D-glucopyranoside (Me-Glc), and methyl α-D-galactopyranoside (Me-Gal) in different space groups. The packing diagrams indicated that IPO might represent a compact tetrameric association in the JRL family. The protomer of IPO showed a canonical β-prism fold with 12 strands of β-sheets but with 2 additional short β-strands at the N terminus. A truncated IPO (ΔN10IPO) by removing the 2 short β-strands of the N terminus was used to reveal its role in a tetrameric association. Gel filtration chromatography confirmed IPO as a tetrameric form in solution. Isothermal titration calorimetry determined the binding constants (KA) of IPO and ΔN10IPO against various carbohydrates. IPO could bind to Me-Man, Me-Glc, and Me-Gal with similar binding constants. In contrast, ΔN10IPO showed high binding ability to Me-Man and Me-Glc but could not bind to Me-Gal. Our structural and functional analysis of IPO revealed that its compact tetrameric association and carbohydrate binding polyspecificity could be regulated by the 2 additional N-terminal β-strands. The versatile carbohydrate binding properties of IPO might play a role in plant defense.

Man-Specific Lectins from Plants, Fungi, Algae and Cyanobacteria, as Potential Blockers for SARS-CoV, MERS-CoV and SARS-CoV-2 (COVID-19) Coronaviruses: Biomedical Perspectives

“…A-K correspond to lectins used as structural scaffolds (( A ): Con A, ( B ): LcA, ( C ): BanLec, ( D ): Morniga-M, ( E ): PPL, ( F ): Heltuba, ( G ): Gastrodianin, ( H ): ASA, ( I ): GNA, ( J ): Nictaba, ( K ): IraB. References [ 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 ,…”

Genome-wide identification and expression analysis of dirigent-jacalin genes from plant chimeric lectins in Moso bamboo (Phyllostachys edulis)

“…Additionally, the conserved aspartic acid of the BL3 linking loop resides in the G-X3-D motif that controls the activity of the lectin and determines the lectin and carbohydrate recognition characteristics of the protein. In addition, a number of other conserved residues and specific amino acid residues have been identified, some of which are specifically involved in sugar binding and quaternary structure formation [83][84][85]. The other three genes with only the GG motif may have undergone base mutations during evolution, so that the sugar-binding site was abolished.…”

Skinning Injury Responses in Sweetpotato

“…Most lectins bind glycoproteins, glycolipids, and polysaccharides (Goldstein and Hayes 1977) and were presumed to assist plants defend themselves against pathogen or insect infestation (Zhu-Salzman et al, 1998;Bandyopadhyay et al, 2001). According to their structures and evolutionary origins, lectins are divided into seven families: legume lectins, type 2 ribosome inactivating proteins, chitin-binding lectins, monocot mannose-binding lectins, cucurbitaceae phloem lectins, jacalin-related lectins (Chang et al, 2012) and others (Damme et al, 1998).…”