A novel phosphorylated glycoprotein in the shell matrix of the oyster Crassostrea nippona

Abstract

We found a novel 52 kDa matrix glycoprotein MPP1 in the shell of Crassostrea nippona that was unusually acidic and heavily phosphorylated. Deduced from the nucleotide sequence of 1.9 kb cDNA, which is likely to encode MPP1 with high probability, the primary structure of this protein shows a modular structure characterized by repeat sequences rich in Asp, Ser and Gly. The most remarkable of these is the DE‐rich sequence, in which continuous repeats of Asp are interrupted by a single Cys residue. Disulfide‐dependent MPP1 polymers occurring in the form of multimeric insoluble gels are estimated to contain repetitive locations of the anionic molecules of phosphates and acidic amino acids, particularly Asp. Thus, MPP1 and its polymers possess characteristic features of a charged molecule for oyster biomineralization, namely accumulation and trapping of Ca2+. In addition, MPP1 is the first organic matrix component considered to be expressed in both the foliated and prismatic layers of the molluscan shell microstructure. In vitro crystallization assays demonstrate the induction of tabular crystals with a completely different morphology from those formed spontaneously, indicating that MPP1 and its polymers are potentially the agent that controls crystal growth and shell microstructure.

Genetic structure and polymorphisms of the N16 gene in Pinctada fucata

“…The motif resides exclusively within the N terminus of YHK-type variants, with the sequence YHKKCGRY, of the B-S group. A GAGs binding motif was first reported in MPP1 (Samata et al, 2008) of the oyster shell OM. In view of molluscan biomineralization, GAGs can provide a highly acidic environment for calcification sites during crystal nucleation.…”

Folian-cv1 Is a Member of a Highly Acidic Phosphoprotein Class Derived From the Foliated Layer of the Eastern Oyster (Crassostrea virginica) Shell and Identified in Hemocytes and Mantle

“…Based on oyster protein structure and activity, synthetic proteins have been produced for use as anti-scalants, dispersants, superabsorbents and many other possible applications (e.g., Wheeler and Koskan, 1993;Sikes and Wierzbicki, 1995). Outside of C. virginica, there appears to be a correlation between the foliated microstructure and the presence of highly phosphorylated matrix proteins (Borbas et al, 1991;Sarashina and Endo, 2001;Samata et al, 2008). However, no causal relationship between this highly phosphorylated matrix and the formation of the foliated microstructure has been established.…”

Intrinsically Disordered Proteins in Biomineralization

“…Several other acidic proteins have been identified from mollusk shells, for instance: MSP-1 (molluskan shell protein 1) from Patinopecten yessoensis (Sarashina& Endo, 2001), Caspartin and Calprismin from Pinna nobilis (Marin et al, 2005), moluskan phosphorylated protein 1 (MPP1) from Crassostrea nippona (Samata et al, 2008), P95 from Unio pictorum (Marie et al, 2008), and Nautilin-63 from Nautilus macromphalus (Marie et al, 2011). No secondary structure analyses of these proteins have been published, hence it is unknown if they are IDPs.…”