Polyphosphoprotein from the Adhesive Pads of Mytilus edulis

• Published in: Biochemistry (Easton) 2001-03, Vol.40 (9), p.2887-2893
• Main Authors: Waite, J. Herbert, Qin, Xiaoxia
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino Acids - analysis; Animals; Base Sequence; Bivalvia - chemistry; Bivalvia - genetics; Chromatography, High Pressure Liquid; DNA, Complementary - chemistry; DNA, Complementary - isolation & purification; Molecular Sequence Data; Mytilus edulis; Phosphoproteins - chemistry; Phosphoproteins - genetics; Phosphoproteins - isolation & purification; Polymerase Chain Reaction; Proteins - chemistry; Proteins - genetics; Proteins - isolation & purification; Sequence Analysis, Protein; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi002718x

Achieving a satisfactory biochemical explanation for the opportunistic underwater adhesion of marine invertebrates such as mussels and barnacles requires a detailed characterization of proteins extracted from holdfast structures produced by these organisms. Mefp-5 is an adhesive protein derived from the foot of the common mussel, Mytilus edulis, and deposited into the byssal attachment pads. Purification and primary structure of mefp-5 was determined by peptide mapping and cDNA sequencing. The protein is 74 residues long and has a mass of about 9500 Da. Mefp-5 composition shows a strong amino acid bias:  aromatic amino acids, lysine, and glycine represent 65 mol % of the composition. More than a third of all the residues in the protein are posttranslationally modified by hydroxylation or phosphorylation. The conversion of tyrosine to 3, 4-dihydroxyphenyl-l-alanine (DOPA) and serine to O-phosphoserine accounts for the hydroxylation and phosphorylation, respectively. Neither modification is complete since variations in the extent of phosphorylation and hydroxylation can be detected by mass spectrometry. More than 75% of the DOPA is adjacent to basic residues, e.g., Lys-DOPA and DOPA-Lys. Phosphoserine occurs in sequences strikingly reminiscent of acidic mineral-binding motifs that appear in statherin, osteopontin, and others. This may be an adaptation for adhesion to the most common substrata for mussels, i.e., calcareous materials.