Neutron crystallographic studies reveal hydrogen bond and water-mediated interactions between a carbohydrate-binding module and its bound carbohydrate ligand

Abstract

Carbohydrate-binding modules (CBMs) are key components of many carbohydrate-modifying enzymes. CBMs affect the activity of these enzymes by modulating bonding and catalysis. To further characterize and study CBM-ligand binding interactions, neutron crystallographic studies of an engineered family 4-type CBM in complex with a branched xyloglucan ligand were conducted. The first neutron crystal structure of a CBM-ligand complex reported here shows numerous atomic details of hydrogen bonding and water-mediated interactions and reveals the charged state of key binding cleft amino acid side chains.