Amino acid sequence and disulphide-bridge pattern of three γ-thionins from Sorghum bicolor

G. Nitti, S. Orru, C. Bloch, L. Morhy, G. Marino, P. Pucci

Research output: Contribution to journalArticle

Abstract

The complete primary structure of a new α-amylase inhibitor from Sorghum bicolor belonging to the γ-thionin family has heen determined and the amino acid sequences of two components of the family already elucidated have been corrected by combining the classical Edman degradation with advanced mass spectrometric procedures. The same integrated approach allowed us to define the pattern of the disulphide bridges in the three isoinhibitors. The arrangement of the cysteine pairing was determined as Cys3-Cys47, Cys14-Cys34, Cys20-Cys41 and Cys24-Cys43. The amino acid sequences of the α-amylase inhibitors share a high degree of similarity with the related plant γ-thionins. All these proteins consist of 47 residues, contain eight cysteine residues forming four disulphide bridges, and show the presence of two clusters of basic amino acids located at both ends of the polypeptide chain. The pattern of S-S bridges determined for the isoinhibitors is identical to that inferred by NMR analysis in two related γ-thionins, thus suggesting a highly conserved organization of the disulphide pairing. These results indicate that the structural similarities among the different γ-thionins extend far beyond the primary structure and possibly concern the secondary structure and the general folding of the entire γ-thionin family.

Original languageEnglish
Pages (from-to)250-256
Number of pages7
JournalEuropean Journal of Biochemistry
Volume228
Issue number2
DOIs
Publication statusPublished - 1995

Keywords

  • γ-thionins
  • disulphide bridges
  • mass spectrometry
  • primary structure

ASJC Scopus subject areas

  • Biochemistry

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