Identification of an "acidic" C-terminal mineral modification sequence from the mollusk shell protein asprich

Sebastiano Collino, Il Won Kim, John Spencer Evans

Research output: Contribution to journalArticle

Abstract

The formation of the mineralized mollusk shell involves the participation specific proteins to control mineral formation and morphology. Recent sequencing studies have identified a subfamily of seven proteins that are specific for the prismatic or calcitic layer of the mollusk Atrina rigida. This subfamily, named Asprich a through g, are polyanionic in sequence and contain conserved sequence regions at the N- and C-termini that are believed to play a role in mineral formation. Using solid-phase peptide synthesis, we have recreated the 42-AA C-terminal domain of Asprich which contains two conserved subdomains, the 17 AA Asp, Glu, Ala repeat (DEAD17) and the Asp, Glu-rich 25 AA acidic-2 region. Using in vitro calcium carbonate mineralization assays, we demonstrate that the 42 AA C-terminal domain exerts effects on the morphology of forming calcite crystals, leading to the formation of porosities and irregular crystal growth. The two subdomains, DEAD17 and acidic-2, exert similar, albeit weaker, effects on crystal growth as well. Interestingly, when DEAD17 and acidic-2 are present as free peptides in a 1:1 mole mixture in parallel mineralization assays, the resulting peptide-mediated effects on calcite morphology are dramatically different from the results obtained for either the 42 AA C-terminal domain or the individual DEAD17 and acidic-2 domains themselves. These results suggest that the functionality of the individual DEAD17 and acidic-2 subdomains can be transformed depending upon the presence of other free peptide species. Structurally, the 42 AA C-terminal domain and the two subdomains are remarkably similar to one another and are conformationally labile, existing in an equilibrium with random-coil and other undefined secondary structures at neutral pH, traits that are also common to calcium carbonate-specific polypeptide sequences.

Original languageEnglish (US)
Pages (from-to)839-842
Number of pages4
JournalCrystal Growth and Design
Volume6
Issue number4
DOIs
StatePublished - Apr 2006

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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