Open AccessThe binding of zinc ions to Emericella nidulans endo‐β‐1,4‐galactanase is essential for crystal formation
Author(s) -
Otten Harm,
Michalak Malwina,
Mikkelsen Jørn Dalgaard,
Larsen Sine
Publication year - 2013
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309113019714
Subject(s) - zinc , hydrolase , glycoside hydrolase , chemistry , crystallization , aspergillus nidulans , stereochemistry , crystal (programming language) , molecule , enzyme , crystallography , biochemistry , organic chemistry , computer science , mutant , programming language , gene
A novel Emericella nidulans endo‐β‐1,4‐galactanase ( En GAL) demonstrates a strong capacity to generate high levels of very potent prebiotic oligosaccharides from potato pulp, a by‐product of the agricultural potato‐starch industry. En GAL belongs to glycoside hydrolase family 53 and shows high (72.5%) sequence identity to an endo‐β‐1,4‐galactanase from Aspergillus aculeatus . Diffraction data extending to 2.0 Å resolution were collected from a crystal of En GAL grown from conditions containing 0.2 M zinc acetate. The crystal structure showed a high similarity between En GAL and other endo‐β‐1,4‐galactanases belonging to GH53. It also revealed 15 zinc ions bound to the protein, one of which is located in the active site, where it is coordinated by residues Glu136 and Glu246 which comprise the catalytic machinery. The majority of the zinc ions are located on the surface of the enzyme, in some cases with side chains from two different molecules as ligands, thus explaining why the presence of zinc ions was essential for crystallization.