Proteomics of the shell matrix proteins and functional analysis of Am13 and AmKaSPI from the shell of Archivesica marissinica.

Archivesica marissinica is a dominant species inhabiting the Haima cold seep in the South China Sea. However, the composition, characterization and specific functions of conserved and unique shell matrix proteins (SMPs) in A. marissinica remain unknown. This study identified 266 shell matrix proteins in A. marissinica. Among them, two conserved SMPs, AmSMP1 protein and Pif-like protein were identified. We have discovered a novel SMP, named Am13, and a highly expressed SMP with a Kazal domain, named AmKaSPI. qPCR analysis revealed Am13 and AmKaSPI are highly expressed in the mantle. Am13 negatively regulated calcite formation and positively regulated aragonite formation. High concentrations of Am13 inhibit aragonite size growth and increase aragonite abundance, possibly due to the limited availability of calcium ions in the deep sea. AmKaSPI positively regulates the formation of both calcite and aragonite by enhancing the nucleation and aggregation and inducing morphology changes in CaCO crystals. AmKaSPI promotes the morphological changes in calcite, forming a cross-shaped star structure, which may the key SMP shaped the "chrysanthemum"-like formation of prism layer. AmKaSPI may facilitate shell formation in A. marissinica in special environments. These findings contribute to a deeper understanding of the composition and characteristics of SMPs in deep-sea clam.