Role of γ-kafirin in the formation and organization of kafirin microstructures

J Agric Food Chem. 2013 Nov 13;61(45):10757-65. doi: 10.1021/jf403571e. Epub 2013 Nov 4.

Abstract

The possible importance of the cysteine-rich γ-prolamin in kafirin and zein functionality has been neglected. The role of γ-kafirin in organized microstructures was investigated in microparticles. Residual kafirin (total kafirin minus γ-kafirin) "microparticles" were non-discrete (amorphous mass of material), as viewed by electron microscopy and atomic force microscopy. Adding 15% γ-kafirin to residual kafirin resulted in the formation of a mixture of non-discrete material and nanosize discrete spherical structures. Adding 30% γ-kafirin to the residual kafirin resulted in discrete spherical nanosize particles. Fourier transform infrared spectroscopy indicated that γ-kafirin had a mixture of random-coil and β-sheet conformations, in contrast to total kafirin, which is mainly α-helical conformation. γ-Kafirin also had a very high glass transition temperature (Tg) (≈270 °C). The conformation and high Tg of γ-kafirin probably confer structural stability to kafirin microstructures. Because of its ability to form disulfide cross-links, γ-kafirin appears to be essential to form and stabilize organized microstructures.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Microscopy, Electron, Scanning
  • Molecular Weight
  • Plant Proteins / chemistry
  • Plant Proteins / ultrastructure*
  • Prolamins / chemistry
  • Protein Structure, Secondary
  • Spectroscopy, Fourier Transform Infrared

Substances

  • Plant Proteins
  • Prolamins
  • kafirin protein, Sorghum bicolor