Study of the conformation of γ-zeins in purified maize protein bodies by FTIR and NMR spectroscopy

Abstract

The gamma-zeins are a mixture of 16, 27, and 50-kDa polypeptides which are important in the formation and stabilization of protein bodies (PB). These organelles are used for deposition of zeins, the water-insoluble storage proteins in maize. The nature of the physical interaction between proteins in the assembly and stabilization of PB are fairly well known. It is suggested the repeated hexapeptide sequence (PPPVHL)(8) in the N-terminus is responsible for aggregation of the gamma-zeins on the PB surface. Despite this importance, there is little information about the native conformation of gamma-zeins. In this work, we have analyzed the secondary structures of gamma-zeins in purified protein bodies from two maize cultivars, in the solid state, by FTIR and NMR spectroscopy. The results revealed that gamma-zeins in their physiological state are comprise similar proportions of alpha-helix and beta-sheet, 33 and 31% as determined by FTIR. It was not possible to state if the polyproline II (PPII) conformation is present in the solid-state structure of gamma-zeins, as has been demonstrated for the hexapeptide in solution. Because of the similarity of the solid-state NMR spectra of gamma and alpha-zeins in the alpha carbon region we attributed their contributions to the beta-sheet structures rather than to the PPII conformation or a mixture of these extended structures.

Formation of a viscoelastic dough from isolated total zein (α-, β- and γ-zein) using a glacial acetic acid treatment

“…Gamma-zein in its physiological state has similar proportions of α-helical and β-sheet structure, 33 and 31%, respectively (Bicudo et al, 2005) and β-zein is predominantly β-sheet in structure (Forato et al, 2003). Hence, the presence of γ-and β-zein in total zein would account for its slightly higher proportion of β-sheet structure.…”

Propriedades mecânicas e molhabilidade de filmes de zeínas extraídas de glúten de milho

“…As proteínas relacionadas a essas bandas têm domínios não repetitivos nos terminais carboxi e amino e repetições homólogas na região central. A Z19 tem 9 blocos de repetições homólogas de 20 aminoácios e a Z22 tem 10 blocos [27] e correspondem à polimorfismos das zeínas-α. O SDS/PAGE do total de proteínas indica que a extração das zeínas se deu de forma satisfatória com a presença de pequena fração de não-zeínas (albumina, globulina e Figura 1.…”

Chemical Characterization of Wood-Leather Panels by Means of 13C NMR Spectroscopy

“…From these spectra, it can be seen that combination and heat treatment resulted in chemical interactions between the components (8). Firstly the amido-carbonyl peak (180 to 170 ppm) broadened on heat treatment with the shoulder at 170 ppm was no longer distinguishable, indicating a change to the proteinaceous component potentially through protein binding or rearrangement (Bicudo et al 2005). An increase in the aliphatic peak (25 to 40 ppm) was observed, which was similarly observed for the modified lignin component in Fig.…”

“…The extracted leather (3) shows a relatively decreased amido-carbonyl, but does not show any significant peak differences in the aliphatic region (25 to 40 ppm) which, anecdotally, would suggest evidence for the presence of lignin as observed with sample 2. Instead, the change in the carbonyl peak may suggest a heat-induced change or rearrangement, although solid state NMR does not readily distinguish protein conformational change (Bicudo et al 2005). Furthermore, the lack of lignin signals in (3) may also be explained by exclusively selecting only pure leather particles with blue spots.…”