title: Shematrin: a family of glycine-rich structural proteins in the shell of the pearl oyster Pinctada fucata.
abstract: Random sequencing of molecules from a cDNA library constructed from mantle mRNA of the pearl oyster Pinctada fucata was used to obtain information on organic matrix proteins in the shell. In the determined sequences, we identified 7 distinct cDNAs encoding similar glycine-rich domains. Complete sequence analysis of these cDNAs showed that the predicted sequences of the proteins, which we named shematrins, possessed similar domains comprising repeat sequences of two or more glycines, followed by a hydrophobic amino acid. In addition, in shematrin-1, -2 and -3, a repeat domain designated as XGnX (where X is a hydrophobic amino acid) was conserved. It is of further note that all the shematrin proteins have RKKKY, RRKKY or RRRKY as their C-terminal sequence. According to northern blot analysis, all shematrins are exclusively expressed in the mantle, and particularly in the edge region of the mantle; furthermore, peptide fragments similar to shematrin-1 and -2 were detected in the prismatic layer of shells by MALDI-TOF/TOF MS analysis. These findings suggest that many of shematrins are synthesized in the mantle edge and secreted into the prismatic layer of the shell, where the protein family is thought to provide a framework for calcification.
authors.affiliation: Wakayama Prefecture Collaboration of Regional Entities for the Advancement of Technological Excellence, Japan Science and Technology Agency, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Yano
authors.forename: Kouhei
authors.initials: K
authors.lastname: Nagai
authors.forename: Koichi
authors.initials: K
authors.lastname: Morimoto
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyamoto
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002113:Calcification, Physiologic / Q000235:genetics*; D003001:Cloning, Molecular; D016326:Extracellular Matrix Proteins / Q000235:genetics* / Q000302:isolation & purification; D015723:Gene Library; D005998:Glycine / Q000235:genetics*; D008969:Molecular Sequence Data; D049911:Pinctada / Q000235:genetics*; D017434:Protein Structure, Tertiary / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D014018:Tissue Distribution
chemical_list: D016326:Extracellular Matrix Proteins; D005998:Glycine