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Vicilin and legumin storage proteins are abundant in water and alkali soluble protein fractions of glandless cottonseed

He Zhongqi, Mattison Christopher P., Zhang Dunhua, Grimm Casey C.
Scientific reports 2021 v.11 no. pp. 9209
albumins, antimicrobial peptides, cottonseed, cottonseed protein, electrophoresis, gossypol, landraces, legumin, oleosin, protein composition, spectroscopy, terpenoids, toxicity, vicilin
The traditional variety of cottonseed contains the toxic terpenoid gossypol and is labeled "glanded cottonseed" as gossypol is deposited in scattered tissue structures called glands. Research efforts have been made to produce a new type of "glandless" cottonseed in which there is only trace gossypol content. Previous work has reported the protein profile of glanded cottonseed protein, but glandless cottonseed protein has not been characterized. In this work, we sequentially extracted water (CSPw)- and alkali (CSPa)-soluble protein fractions from glandless cottonseed. SDS-Gel electrophoresis separated CSPw and CSPa to 8 and 14 dominant protein bands, respectively. Liquid chromatography-electrospray ionization-tandem spectrometry identified peptide fragments of 336 proteins. While the majority of peptides were matched to vicilin and legumin storage proteins, peptides from other functional and uncharacterized proteins were also detected. Compared to glanded samples, we found lower levels (abundance) and types of legumin isoforms, but higher levels and more fragments of vicilin-like antimicrobial peptides in glandless samples. Differences in peptide fragment patterns of 2S albumin and oleosin were also observed between glandless and glanded protein samples. These differences might be due to the higher extraction recovery of proteins from glandless cottonseed as proteins from glanded cottonseed tended to be bound with gossypol, reducing extraction efficiency. The observed differences may also be due in part to an inherent mechanism to offset the gossypol's beneficial antimicrobial properties of glandless cottonseed. This work enriches the fundamental knowledge of glandless cottonseed protein composition. For practical applications, these peptide information will be helpful in better understanding the functional and physicochemical properties of glandless cottonseed protein, and improving their food application potentials.