Model peptide studies of sequence repeats derived from the intracrystalline biomineralization protein, SM50. II. Pro,Asn-rich tandem repeats

Bo Zhang, Guangzhao Xu, John Spencer Evans

Research output: Contribution to journalArticlepeer-review


In the biomineralization process, a number of Pro-rich proteins participate in the formation of three-dimensional supramolecular structures. One such protein superfamily, the Pro, Gly-rich sea urchin intracrystalline spicule matrix proteins, form protein-protein supramolecular assemblies that modify the microstructure of the inorganic mineral phase (calcite) within embryonic sea urchin spicules and adult sea urchin spines. These proteins represent a useful model for understanding Pro sequence usage and the resulting generation of extended or 'open' structures for protein-protein and/or protein-crystal recognition. In the sea urchin spicule matrix protein, SM50 (Strongylocentrotus purpuratus), there exists an unusual 20-residue Pro, Asn-containing repeat, - PNNPNNPNPNNPNNPNNPNP -, which links the upstream 15-residue C-terminal domain and the downstream 211-residue β-spiral repeat domain. To define the structural preferences of this 20-residue repeat, we created a 20-residue N- and C-terminal 'capped' peptidomimetic of this sequence. Using far-uv CD dichroism, CH(α) and α-15N conformational shifts, 3J(NH-CHα) coupling constants, sequential d(NN(i, i + I)) rotating frame nuclear Overhauser effect connectivities, d(αN(i, i + I))/d(NN(i, i + I)) intentsity ratios, amide temperature shift coefficients, amide solvent exchange, and simulated annealing refinement protocols, we have determined that this 20-residue repeat motif adopts an extended 'twist' structure consisting of turn- and coil-like regions. These findings are consistent with previous studies, which have shown that Pro-rich tandem repeats adopt extended, flexible structures in solution. We hypothesize that this 20-residue repeat may fulfill the role of a mineral-binding domain, a protein-protein docking domain, or as an internal 'molecular spacer' for the SM50 protein during spicule biocomposite formation. (C) 2000 John Wiley and Sons, Inc.

Original languageEnglish (US)
Pages (from-to)464-475
Number of pages12
Issue number6
StatePublished - Nov 2000


  • Biomineralization
  • Proline repeats
  • Sea urchin embryo
  • Sea urchine spicule
  • Self-assembly
  • nmr

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Biomaterials
  • Organic Chemistry


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