Aragonite-associated biomineralization proteins are disordered and contain interactive motifs.
BACKGROUND
The formation of aragonite mineral in the mollusk shell or pearl nacre requires the participation of a diverse set of proteins that form the mineralized extracellular matrix. Although self-assembly processes have been identified for several nacre proteins, these proteins do not contain known globular protein-protein binding domains. Thus, we hypothesize that other sequence features are responsible for nacre matrix protein-protein assembly processes and ultimately aragonite biosynthesis.


RESULTS
Of 39 mollusk aragonite-associated protein sequences, 100% contain at least one region of intrinsic disorder or unfolding, with the highest percentages found in framework and pearl-associated proteins relative to the intracrystalline proteins. In some instances, these intrinsically disordered regions were identified as bind/fold sequences, and a limited number correlate with known biomineral-relevant sequences. Interestingly, 95% of the aragonite-associated protein sequences were found to contain at least one occurrence of amyloid-like or cross-β strand aggregation-prone supersecondary motifs, and this correlates with known aggregation and aragonite formation functions in three experimentally tested protein sequences. Collectively, our findings indicate that aragonite-associated proteins have evolved signature sequence traits of intrinsic disorder and aggregation-prone regions that are important for their role(s) in matrix assembly and mineralization.
Laboratory for Chemical Physics, Department of Basic Sciences and Craniofacial Biology, New York University, New York, NY 10012, USA. jse1@nyu.edu
John Spencer
JS
Evans
D000818:Animals; D002113:Calcification, Physiologic; D002119:Calcium Carbonate / Q000737:chemistry* / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000737:chemistry*; D008974:Mollusca / Q000737:chemistry* / Q000378:metabolism; D060734:Nacre / Q000737:chemistry; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D020539:Sequence Analysis, Protein
D016326:Extracellular Matrix Proteins; D060734:Nacre; D002119:Calcium Carbonate