Cross-linking in adhesive quinoproteins: studies with model decapeptides
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Updated: Oct 13, 2026
Isolation of Labile Multi-protein Complexes by in vivo Controlled Cellular Cross-Linking and Immuno-magnetic Affinity Chromatography
Published on: March 9, 2010
1Marine Science Institute/MCDB Department, University of California, Santa Barbara, California 93106, USA.
Abstract:
Mytilus edulis foot protein-1 (mefp1) is a major component of the byssus, an adhesive holdfast in mussels. The recent report of 5, 5'-di(dihydroxyphenyl-L-alanine) (diDOPA) cross-links in byssus [McDowell et al. (1999) J. Biol. Chem. 274, 20293] has raised questions about the relationship of these to mefp1. About 80% of the primary structure of mefp1 consists of a tandemly repeated consensus sequence Ala(1)-Lys(2)-Pro(3)-Ser(4)-Tyr(5)-Pro(6)-Pro(7)-Thr(8)-Tyr(9)-Lys(10 ) with varying degrees of posttranslational hydroxylation to hydroxyprolines in positions 3, 6, and 7 and to DOPA in positions 5 and 9. Six natural or synthetic variants of this decapeptide were subjected to oxidation by tyrosinase or periodate. DOPA is the only residue to suffer losses in all oxidized peptides. Moreover, using MALDI TOF mass spectrometry, oxidized decapeptides all showed evidence of multimer formation and a mass loss of 6 Da per coupled pair of peptides. Multimer formation was inhibited by addition of DOPA-like o-diphenols, but addition of simple amines such as free Lys had no effect. The results are consistent with aryloxy coupling to diDOPA followed by reoxidation to diDOPA quinone. There are subtle but noteworthy variations, however, in multimer formation among the peptide congeners. Decapeptides with Pro(3) modified to trans-4-hydroxyproline do not form multimers beyond dimers; they also exhibit significant Lys losses following oxidation of DOPA. Moreover, in Ala-Lys-Hyp-Ser-Tyr-DiHyp-Hyp-Thr-DOPA-Lys, Tyr appears to be protected from oxidation by tyrosinase.
Insights
Mussel adhesive proteins like mefp1 contain DOPA residues crucial for cross-linking. Oxidation studies reveal DOPA
Area of Science:
- Biochemistry
- Materials Science
- Marine Biology
Background:
- Mytilus edulis foot protein-1 (mefp1) is a key protein in mussel adhesive byssus.
- The presence of 5,5'-di(dihydroxyphenyl-L-alanine) (diDOPA) cross-links in byssus raises questions about their relationship with mefp1.
- Mefp1's structure is dominated by a repeating decapeptide sequence with posttranslational modifications, including DOPA.
Purpose of the Study:
- To investigate the role of DOPA residues in mefp1 cross-linking and multimer formation.
- To explore the relationship between mefp1 structure and the formation of diDOPA cross-links.
- To examine the impact of peptide modifications on oxidation and cross-linking processes.
Main Methods:
- Oxidation of six natural or synthetic mefp1 decapeptide variants using tyrosinase or periodate.
- Analysis of oxidized peptides using MALDI TOF mass spectrometry to detect multimer formation and mass changes.
- Inhibition studies with DOPA-like o-diphenols and simple amines to elucidate cross-linking mechanisms.
Main Results:
- DOPA residues were uniquely lost upon oxidation across all tested peptides.
- Oxidized decapeptides formed multimers with a characteristic mass loss of 6 Da per coupled pair.
- Multimer formation was inhibited by o-diphenols but not by simple amines, suggesting an aryloxy coupling mechanism.
- Specific modifications, like hydroxyproline at position 3, limited multimerization to dimers and affected Lys loss.
- Tyrosinase oxidation of a specific decapeptide variant showed protection of Tyr residues.
Conclusions:
- The results support an aryloxy coupling mechanism involving DOPA oxidation to diDOPA quinone for mefp1 cross-linking.
- Posttranslational modifications in mefp1 significantly influence the extent and nature of peptide cross-linking and multimerization.
- Understanding these cross-linking mechanisms is vital for biomimetic adhesive development.
