title: Cloning and characterization of Prisilkin-39, a novel matrix protein serving a dual role in the prismatic layer formation from the oyster Pinctada fucata.
abstract: Molluscs form their shells out of CaCO(3) and a matrix of biomacromolecules. Understanding the role of matrices may shed some light on the mechanism of biomineralization. Here, a 1401-bp full-length cDNA sequence encoding a novel matrix protein was cloned from the mantle of the bivalve oyster, Pinctada fucata. The deduced protein (Prisilkin-39), which has a molecular mass of 39.3 kDa and an isoelectric point of 8.83, was fully characterized, and its role in biomineralization was demonstrated using both in vivo and in vitro crystal growth assays. Prisilkin-39 is a highly repetitive protein with an unusual composition of Gly, Tyr, and Ser residues. Expression of Prisilkin-39 was localized to columnar epithelial cells of the mantle edge, corresponding to the calcitic prismatic layer formation. Immunostaining in situ and immunodetection in vitro revealed the presence of a characteristic pattern of Prisilkin-39 in the organic sheet and in sheaths around the prisms. Prisilkin-39 binds tightly with chitin, an insoluble polysaccharide that forms the highly structured framework of the shell. Antibody injection in vivo resulted in dramatic morphological deformities in the inner shell surface structure, where large amounts of CaCO(3) were deposited in an uncontrolled manner. Moreover, Prisilkin-39 strictly prohibited the precipitation of aragonite in vitro. Taken together, Prisilkin-39 is the first protein shown to have dual function, involved both in the chitinous framework building and in crystal growth regulation during the prismatic layer mineralization. These observations may extend our view on the rare group of basic matrices and their functions during elaboration of the molluscan shell.
authors.affiliation: Institute of Marine Biotechnology, Department of Biological Sciences and Biotechnology, and Protein Science Laboratory of the Ministry of Education, Tsinghua University, Beijing 100084, China.
authors.forename: Yawei
authors.initials: Y
authors.lastname: Kong
authors.forename: Gu
authors.initials: G
authors.lastname: Jing
authors.forename: Zhenguang
authors.initials: Z
authors.lastname: Yan
authors.forename: Changzhong
authors.initials: C
authors.lastname: Li
authors.forename: Ningping
authors.initials: N
authors.lastname: Gong
authors.forename: Fangjie
authors.initials: F
authors.lastname: Zhu
authors.forename: Dongxian
authors.initials: D
authors.lastname: Li
authors.forename: Yaorun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Guilan
authors.initials: G
authors.lastname: Zheng
authors.forename: Hongzhong
authors.initials: H
authors.lastname: Wang
authors.forename: Liping
authors.initials: L
authors.lastname: Xie
authors.forename: Rongqing
authors.initials: R
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002113:Calcification, Physiologic / Q000502:physiology*; D002119:Calcium Carbonate / Q000737:chemistry; D003001:Cloning, Molecular; D003460:Crystallization; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D049911:Pinctada / Q000033:anatomy & histology / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid
chemical_list: D016326:Extracellular Matrix Proteins; D002119:Calcium Carbonate