Collagen-binding matrix proteins from elastomeric extraorganismic byssal fibers

Biomacromolecules. Nov-Dec 2002;3(6):1240-8. doi: 10.1021/bm0255903.


The byssal threads of marine mussels represent a peculiar case of extraorganismic extracellular material. The threads consist of fibrous chimeric collagens such as preCol-P (with collagenous, elastin-like and histidine-rich domains) embedded in a microfibrillar matrix. We report here on the extraction, purification, and characterization of water-soluble proximal thread matrix protein 1 (PTMP1), which is preferentially located in the proximal portion of each byssal thread and decreases in a proximal to distal direction. PTMP1 has a mass of about 50 kDa as determined by matrix-assisted laser desorption-ionization with time-of-flight (MALDI-TOF) mass spectrometry. Glycine is the most common residue at 12.2 mol %, followed by asparagine/aspartic acid and glutamine/glutamic acid at 11.4 and 9.9 mol %, respectively. Glycosylation has been detected by Western blotting with biotinylated concanavalin A and neutral sugar analysis. With degenerate primers designed from the N-terminal sequence and an additional internal peptide derived by Lys-C endopeptidase digestion, a complete cDNA sequence for this protein was obtained by polymerase chain reaction (PCR) amplification of a Mytilus edulis foot cDNA library. Two variants with minor sequence differences limited to the N-terminus were found. The cDNA-deduced protein sequence reveals two symmetric internal repeats that together account for >85% of the protein. Sequence and epitope similarity of PTMP1 to the A domains of von Willebrand factor and integrin alpha(1)I suggest a capacity for collagen binding. Enzyme-linked immunosorbent assay (ELISA)-based measurement of PTMP1 binding to immobilized type I collagen shows high affinity (apparent K(D) = 0.25 microM), but the binding exhibits no dependence on metals. Using primers designed from M. edulis, we also found a PTMP1-like cDNA in a related species, M. galloprovincialis, with a deduced protein sequence having 97% identity with one M. edulis variant and 99% identity with the other. The corresponding cDNA sequences have 94% and 96% identity, respectively.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Biocompatible Materials / chemistry*
  • Biocompatible Materials / isolation & purification
  • Bivalvia
  • Carbohydrates / analysis
  • Collagen / chemistry*
  • Elastomers
  • Extracellular Matrix Proteins / chemistry*
  • Extracellular Matrix Proteins / genetics
  • Extracellular Matrix Proteins / isolation & purification*
  • Glycoproteins / chemistry
  • Glycoproteins / isolation & purification
  • Immune Sera
  • Immunoassay
  • Male
  • Molecular Sequence Data
  • Protein Binding
  • Rabbits
  • Sequence Alignment
  • Sequence Analysis, DNA
  • Sequence Analysis, Protein
  • von Willebrand Factor / chemistry


  • Biocompatible Materials
  • Carbohydrates
  • Elastomers
  • Extracellular Matrix Proteins
  • Glycoproteins
  • Immune Sera
  • von Willebrand Factor
  • Collagen

Associated data

  • GENBANK/AF414454
  • GENBANK/AY053390
  • GENBANK/AY053391