title: 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.
authors.affiliation: Laboratory of Cell Biology, Faculty of Environmental Health, Azabu University, Sagamihara, Japan. samata@azabu-u.ac.jp
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Samata
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ikeda
authors.forename: Aya
authors.initials: A
authors.lastname: Kajikawa
authors.forename: Hideyoshi
authors.initials: H
authors.lastname: Sato
authors.forename: Chihiro
authors.initials: C
authors.lastname: Nogawa
authors.forename: Daishi
authors.initials: D
authors.lastname: Yamada
authors.forename: Ryo
authors.initials: R
authors.lastname: Yamazaki
authors.forename: Takahiro
authors.initials: T
authors.lastname: Akiyama
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry; D001483:Base Sequence; D002118:Calcium / Q000737:chemistry; D049896:Crassostrea; D003545:Cysteine / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry; D006023:Glycoproteins / Q000737:chemistry*; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
chemical_list: D018076:DNA, Complementary; D004220:Disulfides; D006023:Glycoproteins; D010750:Phosphoproteins; D001224:Aspartic Acid; D003545:Cysteine; D002118:Calcium