Proteins in load-bearing junctions: the histidine-rich metal-binding protein of mussel byssus.

TitleProteins in load-bearing junctions: the histidine-rich metal-binding protein of mussel byssus.
Publication TypeJournal Article
Year of Publication2006
AuthorsZhao, H, Waite, JH
Date Published2006 Nov 28
KeywordsAmino Acid Sequence, Animals, Base Sequence, Bivalvia, Cloning, Molecular, DNA Primers, Metals, Molecular Sequence Data, Periplasmic Binding Proteins, Protein Binding, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Building complex load-bearing scaffolds depends on effective ways of joining functionally different biomacromolecules. The junction between collagen fibers and foamlike adhesive plaques in mussel byssus is robust despite the strikingly dissimilar connected structures. mcfp-4, the matrix protein from this junction, and its presecreted form from the foot tissue of Mytilus californianus were isolated and characterized. mcfp-4 has a mass of approximately 93 kDa as determined by MALDI-TOF mass spectrometry. Its composition is dominated by histidine (22 mol %), but levels of lysine, arginine, and aspartate are also significant. A small amount of 3,4-dihydroxyphenyl-l-alanine (2 mol %) can be detected by amino acid analysis and redox cycling assays. The cDNA-deduced sequence of mcfp-4 reveals multiple variants with highly repetitive internal structures, including approximately 36 tandemly repeated His-rich decapeptides (e.g., HVHTHRVLHK) in the N-terminal half and 16 somewhat more degenerate aspartate-rich undecapeptides (e.g., DDHVNDIAQTA) in the C-terminal half. Incubation of a synthetic peptide based on the His-rich decapeptide with Fe3+, Co2+, Ni2+, Zn2+, and Cu2+ indicates that only Cu is strongly bound. MALDI-TOF mass spectrometry of the peptide modified with diethyl pyrocarbonate before and after Cu binding suggests that histidine residues dominate Cu binding. In contrast, the aspartate-rich undecapeptides preferentially bind Ca2+. mcfp-4 is strategically positioned to function as a macromolecular bifunctional linker by using metal ions to couple its own His-rich domains to the His-rich termini of the preCOLs. Ca2+ may mediate coupling of the C-terminus to other calcium-binding plaque proteins.

Alternate JournalBiochemistry
PubMed ID17115717
PubMed Central IDPMC1892233
Grant ListDE015415 / DE / NIDCR NIH HHS / United States
R01 DE015415 / DE / NIDCR NIH HHS / United States