Fig. 3.

Hyp-arabinogalactan (Hyp–AG) subunits. (A) The linkage connectivity of sugars involved in the repetitive 15-residue consensus Hyp–AG, a conserved structure that accounts for Ca²⁺ binding by classical AGPs (Lamport and Varnai, 2013). A_1–6 arabinose residues; G_1–3 galactose mainchain residues; G_a and G_b, galactose sidedechain residues; R₁ and R₂, rhamnose sidechain residues; GlcA, glucuronic acid sidechain residues; Hyp, hydroxyproline. (B) Three-dimensional molecular model simulating an Hyp–AG with bound Ca²⁺. Hyp–AG interferon Hyp-polysaccharide-1 (IFNHP1) with Ca²⁺ ions (green) bound by two glucuronic acid (GlcA) sidechains (red); the galactan backbone is in dark blue and sidechains in light blue. [Reprinted from Lamport and Varnai (2013).] (C) ‘Molly Cool’ cartoon of an arabinogalactan subunit. Two hands are needed to catch a divalent Ca²⁺ ion. Credits: Amanda Dean and Freyja Dean.