Expression and characterisation of a highly repetitive peptide derived from a wheat seed storage protein

• Published in: Biochimica et biophysica acta Vol. 1479; no. 1; pp. 135 - 146
• Main Authors: Gilbert, Simon M, Wellner, Nikolaus, Belton, Peter S, Greenfield, Julia A, Siligardi, Giuliano, Shewry, Peter R, Tatham, Arthur S
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.06.2000
• Subjects: Amino Acid Sequence; Circular Dichroism; Glutenin; Infrared; Peptides - chemistry; Peptides - genetics; Plant Proteins - chemistry; Polyproline II; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Repetitive Sequences, Amino Acid; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; Triticum - chemistry; TFE, trifluoroethanol; Infrared; ATR, attenuated total reflectance; Polyproline II; FT-IR, Fourier transform infrared; PPII, polyproline II; IPTG, isopropyl- D-thiogalactopyranoside; Glutenin; Circular dichroism; CD, circular dichroism; HMW, high molecular weight
• ISSN: 0167-4838; 0006-3002; 1879-2588
• DOI: 10.1016/S0167-4838(00)00059-5

The high molecular weight (HMW) subunit group of wheat seed storage proteins impart elasticity to wheat doughs and glutens. They consist of three domains: non-repetitive N- and C-terminal domains, which contain cysteine residues for covalent cross-linking, and a central domain consisting of repeated sequences. The circular dichroism and infrared (IR) spectra of an intact HMW subunit were compared with those of a peptide corresponding to the central repetitive domain expressed in Escherichia coli. This allowed the structure of the central domain to be studied in the absence of the N- and C-terminal domains and the contributions of these domains to the structure of the whole protein to be determined. In solution the peptide showed the presence of β-turns and polyproline II-like structure. Variable temperature studies indicated an equilibrium between these two structures, the polyproline II conformation predominating at low temperatures and the β-turn conformation at higher temperatures. IR in the hydrated solid state also indicated the presence of β-turns and intermolecular β-sheet structures. In contrast, spectroscopy of the whole subunit showed the presence of α-helix in the N- and C-terminal domains. The content of β-sheet was also higher in the whole subunit, indicating that the N- and C-terminal domains may promote the formation of intermolecular β-sheet structures between the repetitive sequences, perhaps by aligning the molecules to promote interaction.