In Silico Structural Analysis, Classification, and Functional Annotation of an Uncharacterized Protein from an Aquatic Fungus Lindgomyces ingoldianus

An uncharacterized protein from Lindgomyces ingoldianus was initially annotated to contain various domains with promising biotechnological applications. Thus, this study was conducted to determine the structural characteristics, classification, and potential function of this protein through in silico methods. Results revealed that this protein has a neutral charge and is unstable and non-polar. It is predicted to have a signal peptide, glycoside hydrolase family 114 (GH114) domain, low complexity region, and fungal type cellulose-binding domain (fCBD) or type 1 carbohydrate-binding module (CBM1) region. Structural characterization and phylogenetic analysis revealed that this protein is an endo-α-1,4-polygalactosaminidase enzyme. This protein was also predicted to contain 36 active sites and is extracellularly secreted. Molecular docking analysis showed that it could bind galactosaminogalactan (GAG), a key virulence factor for Aspergillus fumigatus chronic infections. The binding of this protein to GAG was much better than Ega3, which could be attributed to the presence of the fCBD region that is unique to this protein. It is hypothesized that the fCBD domain helps in carbohydrate recognition and holds them in place for maximum catalysis in the GH114 domain. Finally, this protein is found to be related to its orthologue from the plant pathogenic fungus Zopfia rhizophila.