In 2012, we suggested a structural model assigning specific roles for these four proteins and predicting the participation of additional, yet to be identified, proteins in gastrolith formation [12].Our model was based on the division of gastrolith proteins into three functional groups: (1) proteins that are exclusively involved in construction of the chitinous matrix, (2) proteins that are directly involved in the precipitation of the ACC and that have no direct association with chitin, and (3) proteins that participate in both processes (i.e. multi-task proteins). The above-mentioned gastrolith proteins were assigned to the appropriate
group based on sequence analysis and other published empirical data. In addition to assigning potential functions, we suggested the existence of protein–protein interactions involved in the formation of gastrolith protein complexes necessary for attachment of non-chitin-binding proteins
to the organic matrix, as well as for other purposes.