Studies of Storage Proteins of Higher Plants

Abstract

Concanavalin A, the lectin of the Jack bean, Canavalia ensiformis, was extracted and compared with homologous proteins from Canavalia gladiata and Canavalia maritima. All proteins were bound to Sephadex G-100 and eluted from the gel with buffered glucose solution. Quantitative recoveries indicated that large quantities (23 to 28% of dry seed protein) of these lectins are svnthesized by all three species. Antibody preparations made against C. ensiformlis lectin failed to discriminate among the three proteins; the pattern of the precipitin bands indicated identical antigenic determinants in the Ouchterlony doublediffusion assay. Native and sodium dodecyl sulfate polyacrylamide gel electrophoresis also failed to distinguish differences in the proteins. The storage protein active in carbohydrate binding is composed, in each case, of identical subunits. However, the amino acid composition of the subunit chains from the three sources is not identical. In particular, the lectins from C. ensiforrnis and C. gladiata contain two methionine residues per protein subunit, while only one methionine residue is found in the C. martima lectin. Cyanogen bromide cleavage of the puri. fied subunit from C. maritimtia yieded two fragments with molecular weights estimated at 20,400 and 4,600, respectively. Amino acid analysis of the separated fragments indicated that the methionine residue at position 130 in C. ensiformis is absent in the lectin from C. maritima.During seed germination storage proteins are hydrolyzed, and the amino acids are transported into the growing seedling axis. However, certain storage proteins, called lectins and found largely in the cotyledons of legumes, have the capacity to bind specific carbohydrates. The functional significance of this property is unknown, but there have been several reports indicating that lectins have an affinity for the cell surface of species of Rhizobium and may, therefore, facilitate the entry of these symbiotic, nitrogen-fixing organisms into the root cortex (8,18).Relatively little is known about the mechanism of higher plant protein synthesis in comparison to that of microorganisms and animal tissues (38). A cell-free system from higher

Genes and mRNAs Coding for Zein Polypeptides in Zea mays

“…The globin system was chosen because the two hybrids have a similar nucleotide Table 1, applied to the gel. On the sides are the molecular weights of the concanavalin A subunits [65] length and, at least on this basis, the two systems were comparable. The difference of 3 "C accounts for about 1 % of mismatch [48 -501 suggesting a good thermal stability of zein mRNA .…”

Lectinas de sementes como marcadores taxonômicos da tribo Diocleae

“…Suas sementes têm morfologia diversificada e apresentam dentre suas proteínas uma classe que se distingue por mediar a aglutinação de hemácias de vários animais (Hague, 1975;Moreira e Cavada, 1984;De Oliveira et aI., 1990). Esta atividade biológica é inibida pelos açúcares simples como manose, glicose e seus derivados, sendo estas proteÚlas, portanto, classificadas como lectinas (Kocourek e Horejsi, 1983).…”

“…Esta atividade biológica é inibida pelos açúcares simples como manose, glicose e seus derivados, sendo estas proteÚlas, portanto, classificadas como lectinas (Kocourek e Horejsi, 1983). Quando purificadas por cromatografia de afinidade em coluna de Sephadex G-50 e submetidas a eletroforese em gel de poliacrilamida na (Hague, 1975;Moreira e Cavada, 1984;De Oliveira etal., 1990). Embora a função fisiológica destas proteínas seja desconhecida, estudos acerca do seu metabolismo durante a germinação das sementes têm sugerido que elas desempenham papel importante durante o estabelecimento da planta (Kocourek e Horejsi" 1983) e testes imunoquímicos têm demonstrado uma grande semelhança entre elas.…”

Cell-free Synthesis of the Major Storage Protein of the Bean, Phaseolus vulgaris L.

“…An additional advantage to protein studies is the fact that during this growth phase relatively few molecular species are synthesized and accumulated in the maturing cotyledons of these plants. The food value of legume proteins, and the difficulties experienced in enhancing their amino acid balance and protein content, further accentuate the need to understand processes involved in the regulation of biosynthesis of these proteins; studies at the molecular level offer attractive prospects for approaching this goal (10). In previous papers we have described the isolation (15) and characterization (22,23) of Gl globulin.…”