Polyphosphoprotein from the adhesive pads of Mytilus edulis.
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.
Department of Cell Biology, Duke University, Durham, North Carolina 27706, USA. waite@lifesci.ucsb.edu
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D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001483:Base Sequence; D049872:Bivalvia / Q000737:chemistry* / Q000235:genetics; D002851:Chromatography, High Pressure Liquid; D018076:DNA, Complementary / Q000737:chemistry / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D020539:Sequence Analysis, Protein; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D000596:Amino Acids; D018076:DNA, Complementary; D010750:Phosphoproteins; D011506:Proteins; C037403:adhesive protein, mussel