Expression and characterisation of a highly repetitive peptide derived from a wheat seed storage protein.
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 beta-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 beta-turn conformation at higher temperatures. IR in the hydrated solid state also indicated the presence of beta-turns and intermolecular beta-sheet structures. In contrast, spectroscopy of the whole subunit showed the presence of alpha-helix in the N- and C-terminal domains. The content of beta-sheet was also higher in the whole subunit, indicating that the N- and C-terminal domains may promote the formation of intermolecular beta-sheet structures between the repetitive sequences, perhaps by aligning the molecules to promote interaction.
Gilbert
S M
SM
IACR-Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, UK.
Wellner
N
N
Belton
P S
PS
Greenfield
J A
JA
Siligardi
G
G
Shewry
P R
PR
Tatham
A S
AS
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D010455:Peptides / Q000737:chemistry* / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D020449:Repetitive Sequences, Amino Acid; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D014908:Triticum / Q000737:chemistry*
D010455:Peptides; D010940:Plant Proteins; D011994:Recombinant Proteins