In Silico Characterization of the Physicochemical and Biological Properties of the Pink (Pleurotus djamor var. salmoneostramineus) Oyster Mushroom Chromoprotein

Cap color is an important commercial trait for oyster mushrooms. Various pigment constituents determine a diverse color. However, the pigments of oyster mushrooms are still ambiguous. The pink oyster mushroom (Pleurotus salmoneostramineus or Pleurotus djamor) chromoprotein is one of the few proteins belonging to this fungus that has a record of its sequence of amino acid residues. However, even though there are studies about this chromoprotein isolation, purification, and crystallization, the current information focused on its 3-dimensional model and the cofactor and prosthetic group (3H-indol-3-one) binding sites is unreliable and fragmented. Therefore, in this study, using free online servers such as Prot pi, GalaxyWEB, MIB, and CB-Dock2, a structural analysis and the prediction of its physicochemical and biological properties were conducted, to understand the possible function of this chromoprotein. The obtained results showed that this molecule is a protein with a molecular weight of 23 712.5 Da, an isoelectric point of 7.505, with oligomerization capacity in a dimer and glycation in the Ser6 residue. In addition, the participation of the residues Leu5, Leu8, Lys211, Ala214, and Gln215 in the binding of the prosthetic group to the protein was highlighted; as well as Ser6 and Pro7 are important residues for the interaction of the Mg²⁺ ion and eumelanin. Likewise, morphological changes based on different culture conditions (light/dark) showed that this protein is constitutive expressed and independent of blue light. The findings in this study demonstrate that pink chromoprotein is a melanosomal protein, and it possibly has a critical role in melanogenesis and the melanin polymerization. However, more experimental studies are needed to predict a possible mechanism of action and type of enzymatic activity.