The cellulose binding mechanism of a novel cellulose binding domain from the brown-rot fungus Gloeophyllum trabeum

IRG/WP 23-11021

M Aoki, Y Kojima, M Wada, M Yoshida

In nature, wood decay is caused by various wood-rotting basidiomycetes. Wood-rotting basidiomycete are mainly divided into white-rot fungi and brown-rot fungi. Their main carbon source is cellulose of the wood cell wall during wood decay, and they produce a variety of enzymes to decompose cellulose. The cellulolytic enzymes often possess a cellulose binding domain (CBD) as an additional domain connected to catalytic domain. Fungal CBDs have been classified into Carbohydrate-Binding Module Family 1 (CBM1) in the Carbohydrate-Active enzyme (CAZy) database. Since the removal of CBM1 in cellobiohydrolase (CBH), which is essential enzyme for the degradation of crystalline cellulose, decreased the degradation activity of crystalline cellulose but not the degradation of amorphous cellulose, the binding domain have been considered to be critical for crystalline cellulose degradation by CBH. From the results of genetic analysis, it have been known that almost brown-rot fungi lack CBM1. In our previous study, however, it was found that uncharacterized C-terminal domain in a lytic polysaccharide monooxygenase from the brown-rot fungus Gloeophyllum trabeum had binding ability to native celluloses, although the amino acid sequence of this domain shows no homology to any known CBDs. Therefore, we hypothesized that this novel CBD from G. trabeum (GtCBD) has a different mechanism of cellulose binding from CBM1. To obtain the knowledge of cellulose binding mechanism in GtCBD, in this study, we carried out the site-directed mutagenesis analysis to identify the amino acid residues which are involved in adsorption to cellulose. The research provides a new insight for cellulose binding mechanism of CBD.


Keywords: crystalline cellulase, cellulose binding domain

Conference: 23-05-28/06-01 Cairns, Australia


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