1 Amyloid Assembly Endows Gad m 1 with 2 Biomineralization Properties 3

Acid proteins capable of nucleating Ca2+ and displaying aggregation capacity play key 13 roles in the formation of calcium carbonate biominerals. EF-hands are among the largest 14 Ca2+-binding motif in proteins. Gad m 1, an Atlantic cod β-parvalbumin isoform, is a monomeric 15 EF-hand protein that acts as a Ca2+ buffer in fish muscle and is able to form amyloids under acidic 16 conditions. Since nucleating Ca2+ protein have a propensity to form extended β-strand structures, 17 we wondered whether amyloid assemblies of a protein containing refolded EF-hand motifs were 18 able to influence the in vitro calcium carbonate crystallization. Here we have used the Gad m 1 19 chain as model to generate monomeric and amyloid assemblies and analyze their effect on in vitro 20 calcite formation. We found that only amyloid assemblies alter calcite morphology. 21