The Structural Characterization and Antipathogenic Activities of Quinoin, a Type 1 Ribosome-Inactivating Protein from Quinoa Seeds

Abstract

Quinoin is a type 1 ribosome-inactivating protein (RIP) we previously isolated from the seeds of pseudocereal quinoa (Chenopodium quinoa) and is known as a functional food for its beneficial effects on human health. As the presence of RIPs in edible plants could be potentially risky, here we further characterised biochemically the protein (complete amino acid sequence, homologies/differences with other RIPs and three-dimensional homology modeling) and explored its possible defensive role against pathogens. Quinoin consists of 254 amino acid residues, without cysteinyl residues. As demonstrated by similarities and homology modeling, quinoin preserves the amino acid residues of the active site (Tyr75, Tyr122, Glu177, Arg180, Phe181 and Trp206; quinoin numbering) and the RIP-fold characteristic of RIPs. The polypeptide chain of quinoin contains two N-glycosylation sites at Asn115 and Asp231, the second of which appears to be linked to sugars. Moreover, by comparative MALDI-TOF tryptic peptide mapping, two differently glycosylated forms of quinoin, named pre-quinoin-1 and pre-quinoin-2 (~0.11 mg/100 g and ~0.85 mg/100 g of seeds, respectively) were characterised. Finally, quinoin possesses: (i) strong antiviral activity, both in vitro and in vivo towards Tobacco Necrosis Virus (TNV); (ii) a growth inhibition effect on the bacterial pathogens of plants; and (iii) a slight antifungal effect against two Cryphonectria parasitica strains.

Cytotoxicity Effect of Quinoin, Type 1 Ribosome-Inactivating Protein from Quinoa Seeds, on Glioblastoma Cells

“…In this framework, quinoin, similar to saporin-6 [21,24,31], is an attractive archetype of this toxin family and could represent a novel tool in biomedicine. Data reported in this work are the starting point for its possible use in neuroscience and in tumor therapy.…”

“…A clear potential of this strategy is given by saporin-6, a type 1 RIP isolated from Saponaria officinalis seeds. This protein, similar to quinoin [31], is very used in several conjugates in neuroscience as a convenient tool to induce highly selective degeneration of a desired cell subpopulation. Indeed, saporin-based toxins, inducing selective cell death, are one of the approaches used to study (i) neurodegenerative diseases, (ii) the functions of certain cell subpopulations in the brain, and (iii) the development of alternative therapies [21].…”

A Novel EGFR Targeted Immunotoxin Based on Cetuximab and Type 1 RIP Quinoin Overcomes the Cetuximab Resistance in Colorectal Cancer Cells

“…seeds [ 24 ], which possesses a low IC 50 in vitro (5.08 pM; 0.15 ng/mL) [ 25 ] similar to saporin S6, a type 1 RIP isolated from Saponaria officials L. seeds (IC 50 = 37 pM; 1.09 ng/mL), the latter widely used for immunoconjugate production [ 26 ]. Quinoin is a very stable (Tm = 68.2 °C) and basic protein of 254 amino acid residues, without cysteinyl residues [ 27 ]. In addition, this type 1 RIP possesses cytotoxic effects towards several human malignant cell lines by activating the apoptosis pathway [ 24 , 28 ] and exhibits antifungal activity against the green mould Penicillium digitatum [ 25 ].…”

Avaliação da qualidade proteica, peso de órgãos e comprimento da tíbia e animais experimentais alimentados com quinoa (Chenopodium, quinoa)

“…Devido à sua alta qualidade nutricional, vem despertando a atenção de pesquisadores em várias partes do mundo. 1,2 Os cientistas estão mostrando interesse pela qualidade nutricional, devido ao alto teor de proteína (≈15%), com um equilíbrio certo de aminoácidos essenciais, alto teor de vitaminas e também compostos nutracêuticos, como flavonoides. 2,3 Suas sementes contêm altos níveis de fotoquímicos, como fenólicos, peptídeos ou oligossacarídeos.…”

“…12 Outra vantagem da proteína da quinoa é que ela apresenta algumas características desejáveis do ponto de vista de processamento de alimentos, já que possui adequada propriedade de gelatinização, capacidade de absorção de água e de emulsificação, além da estabilidade (resistência à retrogradação). [1][2][3][5][6][7] Estes são aspectos muito interessantes para o desenvolvimento de novos produtos, inclusive da elaboração de produtos para indivíduos portadores de doença celíaca, já que o maior problema da substituição dos cereais que contêm glúten por outras matérias-primas que não o contêm é a ausência dessas características. 11 Diante do exposto, o objetivo deste trabalho foi avaliar a qualidade proteica da quinoa real (Chenopodium quinoa) e os efeitos de sua ingestão no peso do fígado, baço e comprimento da tíbia em ratos.…”