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Unraveling the multivalent binding of a marine family 6 carbohydrate‐binding module with its native laminarin ligand
Author(s) -
Jam Murielle,
FickoBlean Elizabeth,
Labourel Aurore,
Larocque Robert,
Czjzek Mirjam,
Michel Gurvan
Publication year - 2016
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.13707
Subject(s) - laminarin , isothermal titration calorimetry , carbohydrate binding module , protein data bank (rcsb pdb) , chemistry , biochemistry , ligand (biochemistry) , polysaccharide , binding site , carbohydrate , stereochemistry , receptor , glycoside hydrolase , hydrolysis
Laminarin is an abundant brown algal storage polysaccharide. Marine microorganisms, such as Zobellia galactanivorans , produce laminarinases for its degradation, which are important for the processing of this organic matter in the ocean carbon cycle. These laminarinases are often modular, as is the case with Zg LamC which has an N‐terminal GH 16 module, a central family 6 carbohydrate‐binding module ( CBM ) and a C‐terminal Por SS module. To date, no studies have characterized a true marine laminarin‐binding CBM 6 with its natural carbohydrate ligand. The crystal structure of Zg LamC CBM6 indicates that this CBM has two clefts for binding sugar (variable loop site, VLS ; and concave face site, CFS ). The Zg LamC CBM6 VLS binds in an exo‐manner and the CFS interacts in an endo‐manner with laminarin. Isothermal titration calorimetry (ITC) experiments on native and mutant Zg LamC CBM6 confirm that these binding sites have different modes of recognition for laminarin, in agreement with the ‘regional model’ postulated for CBM 6‐binding modules. Based on ITC data and structural data, we propose a model of Zg LamC CBM6 interacting with different chains of laminarin in a multivalent manner, forming a complex cross‐linked protein–polysaccharide network. Database PDB code 5FUI .