The Complete Primary Structure of Molluscan Shell Protein 1 (MSP-1), an Acidic Glycoprotein in the Shell Matrix of the Scallop Patinopecten yessoensis |
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Authors: | Isao Sarashina Kazuyoshi Endo |
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Institution: | (1) Department of Earth and Planetary Sciences, University of Tokyo, Tokyo 113-0033, Japan, JP |
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Abstract: | The complete primary structure of MSP-1, a major water-soluble glycoprotein in the foliated calcite shell layer of the scallop
Patinopecten yessoensis, is reported. The full-length complementary DNA for MSP-1 isolated by polymerase chain reaction contained a sequence for a
signal peptide of 20 amino acids followed by a polypeptide of 820 amino acids with calculated molecular mass of 74.5 kDa.
The deduced amino acid sequence of MSP-1 includes a high proportion of Ser (32%), Gly (25%), and Asp (20%), and the predicted
isoelectric point is 3.2; in these respects, MSP-1 is a typical acidic glycoprotein of mineralized tissues. A repeated modular
structure characterizes MSP-1, with a sequence unit between 158 and 177 amino acids in length being repeated 4 times in tandem
in the middle part of the protein. The repeated unit comprises 3 modules (SG, D, and K domains), each having a distinct amino
acid composition and sequence. The SG domain is almost exclusively composed of Ser and Gly residues. The D domain is rich
in Asp residues, potential N-glycosylation and phosphorylation sites. The K domain is rich in Gly residues and has a core of basic residues. The Asp residues
are arranged more or less regularly in the D domains, exhibiting some repeated motifs such as Asp-Gly-Ser-Asp and Asp-Ser-Asp.
Further, the 4 D domains indicate remarkable overall sequence similarities to each other. These observations suggest that
the regular arrangements of COO− groups in the D domain side chains may be important for specific control of crystal growth.
Received September 19, 2000; accepted February 9, 2001 |
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Keywords: | : acidic shell protein biomineralization calcite mollusks MSP-1 primary structure |
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