A PL7 alginate lyase caught with an alginate chain in its grip. Drag to rotate. Scroll to zoom.
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Crystal structure of a PL7 alginate lyase reveals the molecular architecture enabling polysaccharide degradation. The enzyme displays the characteristic β-jelly roll fold (green β-sheets) flanked by peripheral α-helices (blue). A deep substrate-binding groove (semitransparent surface) cradles the alginate chain (yellow sticks), positioning it for catalysis. Key catalytic residues (red sticks, labelled) — Arg146, Gln189, His191 and position 284 — line the groove, with His191 acting as general base and the residue at 284 as general acid during β-elimination. Structure: PDB 2ZAB, alginate lyase A1-II′ from Sphingomonas sp. A1, captured as the substrate-trapped Y284F variant (Tyr284→Phe, which halts cleavage so the bound alginate can be seen).