Study of wheat high molecular weight 1D x 5 subunit by 13 C and 1 H solid‐state NMR. II. Roles of nonrepetitive terminal domains and length of repetitive domain

• Published in: Biopolymers Vol. 65; no. 2; pp. 158 - 168
• Main Authors: Alberti, Enrica, Gilbert, Simon M., Tatham, Arthur S., Shewry, Peter R., Naito, Akira, Okuda, Kanna, Saitô, Hazime, Gil, Ana M.
• Format: Journal Article
• Language: English
• Published: 15.10.2002
• ISSN: 0006-3525; 1097-0282
• DOI: 10.1002/bip.10212

Abstract This work follows a previous article that addressed the role of disulfide bonds in the behavior of the 1D x 5 subunit upon hydration. Here the roles of nonrepetitive terminal domains present and the length of the central repetitive domain in the hydration of 1D x 5 are investigated. This was achieved by comparing the hydration behavior of suitable model samples determined by 13 C‐ and 1 H‐NMR: an alkylated 1D x 5 subunit ( alk 1D x 5), a recombinant 58‐kDa peptide corresponding to the central repetitive domain of 1D x 5 (i.e., lacking the terminal domains), and two synthetic peptides (with 6 and 21 amino acid residues) based on the consensus repeat motifs of the central domain. The 13 C cross‐polarization and magic angle spinning (MAS) experiments recorded as a function of hydration gave information about the protein or peptide fractions resisting plasticization. Conversely, 13 C single pulse excitation and 1 H‐MAS gave information on the more plasticized segments. The results are consistent with the previous proposal of a hydrated network held by hydrogen‐bonded glutamines and possibly hydrophobic interactions. The nonrepetitive terminal domains were found to induce water insolubility and a generally higher network hindrance. Shorter chain lengths were shown to increase plasticization and water solubility. However, at low water contents, the 21‐mer peptide was characterized by higher hindrance in the megahertz and kilohertz frequency ranges compared to the longer peptide; and a tendency for a few hydrogen‐bonded glutamines and hydrophobic residues to remain relatively hindered was still observed, as for the protein and large peptide. It is suggested that this ability is strongly dependent on the peptide primary structure. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 65: 158–168, 2002