Synthesis and characterization of water-soluble silk peptides and recombinant silk protein containing polyalanine, the integrin binding site, and two glutamic acids at each terminal site as a possible candidate for use in bone repair materials

Biomacromolecules. 2013 Oct 14;14(10):3731-41. doi: 10.1021/bm401118m. Epub 2013 Sep 19.

Abstract

The recombinant proteins [EE(A)12EETGRGDSPAAS]n (n = 5,10) were prepared as a potential scaffold material for bone repair. The construct was based on Antheraea perni silk fibroin to which cells adhere well and combined poly(alanine), the integrin binding site TGRGDSPA, and a pair of glutamic acids (E2) at both the N- and C-terminal sites to render the construct water-soluble and with the hope that it might enhance mineralization with hydroxyapatite. Initially, two peptides E2(A)nE2TGRGDSPAE2(A)nE2 (n = 6, 12) were prepared by solid state synthesis to examine the effect of size on conformation and on cell binding. The larger peptide bound osteoblasts more readily and had a higher helix content than the smaller one. Titration of the side chain COO(-) to COOH of the E2 and D units in the peptide was monitored by solution NMR. On the basis of these results, we produced the related recombinant His tagged protein [EE(A)12EETGRGDSPAAS]n (n = 5,10) by expression in Escherichia coli . The solution NMR spectra of the recombinant protein indicated that the poly(alanine) regions are helical, and one E2 unit is helical and the other is a random coil. A molecular dynamics simulation of the protein supports these conclusions from NMR. We showed that the recombinant protein, especially, [EE(A)12EETGRGDSPAAS]10 has some of the properties required for bone tissue engineering scaffold including insolubility, and evidence of enhanced cell binding through focal adhesions, and enhanced osteogenic expression of osteoblast-like cells bound to it, and has potential for use as a bone repair material.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Bone Substitutes / chemistry*
  • Cell Adhesion
  • Cell Line
  • Fibroins / chemical synthesis
  • Fibroins / chemistry*
  • Fibroins / metabolism*
  • Glutamates / analysis*
  • Hydrogen-Ion Concentration
  • Integrins / metabolism*
  • Mice
  • Molecular Dynamics Simulation
  • Moths
  • Nuclear Magnetic Resonance, Biomolecular
  • Osteoclasts / chemistry
  • Osteoclasts / cytology
  • Peptides / analysis*
  • Protein Conformation
  • Recombinant Proteins / chemical synthesis
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Solubility
  • Surface Properties
  • Water / chemistry

Substances

  • Bone Substitutes
  • Glutamates
  • Integrins
  • Peptides
  • Recombinant Proteins
  • Water
  • polyalanine
  • Fibroins