A Novel Accessory Protein ArCel5 from Cellulose-Gelatinizing Fungus Arthrobotrys sp. CX1

Improved understanding of the mechanism of cellulose pretreatment by accessory proteins is beneficial for increasing the hydrolysis efficiency of cellulosic substrates. Here, we report a protein ArCel5 isolated from the cellulose-gelatinizing fungus Arthrobotrys sp. CX1. ArCel5 with lower specific hydrolysis activity could effectively disrupt the structure of filter paper and might function as an accessory protein. ArCel5 is a multi-domain protein including a CBM1 family carbohydrate-binding module, a glycosylation linker, and a GH5 family catalytic domain. Based on analyses of adsorption capacity, SEM, hydrature index, FTIR, XRD, and synergistic activity, we demonstrated that CBM1 and linker played an essential role in the binding affinity of the protein and the decrystallization of filter paper, which further encouraged the synergistic action between ArCel5 and cellulases. Notably, glycosylation modification further strengthened the function of the linker region. Overall, the results of this study provide insight into the cellulose decrystallization mechanism of a novel accessory protein ArCel5 that will benefit future applications.