Prophenoloxidase (ProPO) cascade is a principal defense system in crustaceans, which consists of a variety of pattern recognition proteins (lipopolysaccharide and beta-glucan-binding protein [beta-GBP], beta-GBP, and beta-glucan recognition protein), proteases (serine protease), and protease inhibitors (alpha 2-macroglobulin and pacifastin) to regulate the protection mechanism in crustaceans. In the prophneoloxidase pathway, the protein-protein interactions (PPIs) and other immune-related analyses still have not been reported. Moreover, the structural features of ProPO cascade proteins have not yet been reported, hence we constructed the three-dimensional structural features for all ProPO pathway proteins. Their PPIs were studied through an in silico approach. Laminarin has been identified as a triggering activator and it showed energetic binding with homology modeled beta-GBP and activated the beta-GBP, followed by the protein-protein complex formation leading to phenoloxidase synthesis. These findings provided a novel view of the ProPO mechanism and enhanced our knowledge of the innate immune system in crustaceans via computation. In conclusion, we propose a combined experimental and computational approach to analyze the mechanism of ProPO cascade proteins. (C) 2015 International Union of Biochemistry and Molecular Biology, Inc. Volume 63, Number 6, Pages 779-788, 2016