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[Pathogen-induced plant proteins].

Pathogen-induced plant proteins are classified by their functional characteristics: (a) involvement in plant cell signaling; (b) inhibition of enzymes excreted by the pathogens; (c) stabilization of plant cell walls or ability to trigger apoptosis; (d) enzymatic activity producing lysis of cell walls of pathogenic fungi and bacteria; (e) enzymatic activity in metabolic pathways of phenylpropane and terpene phytoalexins; and (f) ability to affect the pathogens directly, by disturbing the function of their cell membranes or by inactivating their ribosomes. Examples of transgenic plants with increased immunity against pathogens are also provided.

Plant Cells↗

Modification of plant proteins by immobilized proteases.

A potential application of plant proteins could be a replacement of animal proteins now in use in the food industry on the basis of certain specific functional properties plant proteins have. Modification of the chemical structure of selected plant proteins is needed to replace more expensive animal proteins as food ingredients that have specific functional characteristics. Structure modification may be achieved by physical, chemical, or microbiological methods, or by a combination of these. Immobilized enzyme techniques offer significant advantages for protein modification. Knowledge of the molecular properties of plant proteins is essential to understand the basis of protein functionality, to modify proteins so that they acquire desirable functional properties, and to predict potential applications of modified plant proteins. This paper reviews all the above mentioned aspects of plant protein chemistry and potential utilization.

Amino Acids↗

[The effect of extremely low doses of the novel regulatory plant proteins ].

Searching and study on regulatory proteins, which can keep under control the scope of important processes as like as cell adhesion, proliferation, differentiation and morphogenesis, is an actual aim of the current biochemistry. Recently we have identified S-100 proteins in plants of following species: plantain (Plantago major L.), aloe (Aloe arborescens L.), and bilberry (Vaccinum myrtillus L.). Extraction and purification of S-100 proteins gotten from these plants were performed by the method we developed earlier for adhesion proteins of animal tissues. Homogeneity of the studied plant proteins was evaluated and confirmed by HPLC and SDS-electrophoresis in PAAG. Both, plant and animal proteins have appeared to be biologically active at extremely low doses. The tests were performed by adhesiometrical method in short-term tissue culture of mouse's liver in vitro. As a result it was established that the plant proteins insert a membranotropic effect being added in extremely low doses, corresponding to 10(-10)-10(-13) mg/ml. Keeping in mind that the plantain is well known remedy for wound protection and healing, in several experiments we studied the biological effect of plant S-100 proteins on animal cells. It was found that S-100 proteins obtained from plantain influences proliferation of human fibroblasts in vitro. It was found that after the treatment with this protein in low doses the cell growth rate increases essentially.

Aloe↗

Effects of dietary animal and plant proteins on the cholesterol metabolism in immature and mature rats.

Three- and 9-mo-old rats were fed purified diets that contained either casein, cottonseed or soybean protein for 28 d, and plasma total and high density lipoprotein (HDL) cholesterol, lecithin cholesterol acyltransferase (LCAT) activity and excretion of fecal neutral sterols were measured. These analyses were performed in order to examine how various dietary proteins from animal and plant sources fed in a purified diet influence the changes in the cholesterol metabolism of the young and old rats. Both immature (3-mo-old) and mature (9-mo-old) rats fed purified diet containing casein maintained significantly higher plasma total and HDL cholesterol levels than their counterparts fed the same diets but containing plant proteins (soybean and cottonseed). The fractional rate of esterification (FR) of plasma free cholesterol in mature casein-fed rats was lower than that in immature rats. The FR was also lower in immature rats fed casein than in those fed plant protein. The net turnover rate (NR) of plasma cholesteryl esters (CE) tended to be higher in mature rats and in general was not affected by the dietary protein source. The rate of fecal excretion of neutral sterols was significantly higher in immature rats than in mature rats and in animals fed plant proteins at both ages than in those fed casein.

Aging↗

Generation of plant protein microarrays and investigation of antigen-antibody interactions.

The application of proteomics methods, such as the protein microarray technology, in plant science has been strongly supported by the completion of genome sequencing projects of Arabidopsis thaliana and rice. In this chapter we describe a method to generate plant protein microarrays and to use them for characterizing monoclonal antibodies or polyclonal sera with regard to their specificity and cross-reactivity. The method starts with characterized E. coli cDNA expression clones encoding His-tagged plant proteins. After expression and purification of these recombinant proteins in high throughput, protein microarrays are generated utilizing a contact printer. For the detection of the recombinant proteins on the microarrays, an anti-RGS-His6 antibody is used. To characterize specific antibodies, the microarrays are incubated with the respective antibody solutions followed by fluorescently labeled secondary antibodies. Signal detection is performed by means of an arrayscanner system. Protein microarrays containing the whole proteome of a plant will represent the ideal format to test antibody specificity and cross-reactivity in the future.

Antibody Specificity↗

Protein utilization by young women consuming animal or plant protein diets at various levels of vitamin B-6 intake.

Eight young women consumed a vitamin B-6 depletion diet (egg albumen formula, less than 0.05 mg vitamin B-6/d) for 11-28 d. Subjects (n = 4) then consumed either animal protein (AP, mainly dairy and poultry products) or plant protein (PP, mainly various types of beans) diets with increasing vitamin B-6 intake (0.5, 1.0, 1.5, and 2.0 mg/d) for periods of 14-21 d. All diets provided 1.55 g protein/kg body wt. Apparent protein digestibility of AP (94.6%) was significantly higher than that of PP (88.4%) diets (p less than 0.001). Protein digestibility was not significantly affected by vitamin B-6 intake. Apparent nitrogen balance of subjects consuming AP diets was slightly, though not significantly, higher than that of subjects fed PP diets. N balance was not influenced by vitamin B-6 intake. Data suggest that short-term low vitamin B-6 intake does not affect protein utilization in humans as determined by digestibility and N balance.

Adult↗

Gastrodianin-like mannose-binding proteins: a novel class of plant proteins with antifungal properties.

The orchid Gastrodia elata depends on the fungus Armillaria mellea to complete its life cycle. In the interaction, fungal hyphae penetrate older, nutritive corms but not newly formed corms. From these corms, a protein fraction with in vitro activity against plant-pathogenic fungi has previously been purified. Here, the sequence of gastrodianin, the main constituent of the antifungal fraction, is reported. Four isoforms that encoded two different mature proteins were identified at the cDNA level. Another isoform was detected in sequenced peptides. Because the antifungal activity of gastrodianins produced in and purified from Escherichia coli and Nicotiana tabacum was comparable to that of gastrodianin purified from the orchid, gastrodianins are the active component of the antifungal fractions. Gastrodianin accumulation is probably an important part of the mechanism by which the orchid controls Armillaria penetration. Gastrodianin was found to be homologous to monomeric mannose-binding proteins of other orchids, of which at least one (Epipactis helleborine mannose-binding protein) also displayed in vitro antifungal activity. This establishes the gastrodianin-like proteins (GLIPs) as a novel class of antifungal proteins.

Amino Acid Sequence↗

Molecular cloning of a Chinese hamster mitochondrial protein related to the "chaperonin" family of bacterial and plant proteins.

The complete cDNA sequence of a mitochondrial protein from Chinese hamster ovary cells, designated P1, which was originally identified as a microtubule-related protein (Gupta, R.S., Ho, T.K.W., Moffat, M.R.K., and Gupta, R. (1982) J. Biol. Chem. 257, 1071-1078), has been determined. The P1 cDNA encodes a protein of 60,983 Da including a 26-amino acid putative mitochondrial targeting sequence at its N-terminal end. The deduced amino acid sequence of Chinese hamster P1 shows 97% identity to the human P1 protein. Most interestingly, the amino acid sequences of mammalian P1 proteins show extensive sequence homology (42-60% identical residues and an additional 15-25% conservative replacements) to the "chaperonin" family of bacterial, yeast, and plant proteins (viz. groEL protein of Escherichia coli, hsp 60 protein of yeast, and ribulose-1,5-bisphosphate carboxylase subunit binding protein of plant chloroplasts) and to the 60-65-kDa major antigenic protein of mycobacteria and Coxiella burnetii. The homology between mammalian P1 and other proteins begins after the putative mitochondrial presequence and extends up to the C-terminal end. Furthermore, similar to the chaperonin family of proteins, P1 appears to exist in cells as a homooligomeric complex of seven subunits and shows ATPase activity. These observations strongly indicate that P1 protein is a member of the chaperonin family and that it may be involved in a similar function in mammalian cells.

Adenosine Triphosphatases↗

Structural studies on native and chemically modified storage proteins from rapeseed (Brassica napus L.) and related plant proteins.

Recent data on the structure and chemical modification of the two main storage proteins of rapeseed, the high-molecular mass 12 S globulin and the low-molecular mass 2 S protein (napin) are summarized and compared with those of related seed proteins. The 12 S globulin is built up of six subunits forming a quaternary structure which can be approximated by the model of a trigonal antiprism. The subunits, composed of a larger and a smaller polypeptide chain each, have a two-domain structure which is typical for all related plant proteins. These are characterized by a sedimentation coefficient of 11-13 S, a molecular mass of 300,000-360,000 g/mol and a high percentage of beta-sheet conformation. Increasing succinylation results in a step-by-step dissociation up to the subunits and to an unfolding of the latter at a critical level of modification amounting to 60-70%. These structural changes affect the functional properties remarkably. The napin fraction comprises a group of closely related and highly basic proteins with molecular masses of 12,000-14,000 g/mol, a high content of sulphur-containing amino acids and rich in helical conformation. They are built up of a larger and a smaller disulphide bridged polypeptide chain. Acylation does not abolish the secondary or tertiary structure which are stabilized by inter- and intrachain disulphide bonds. Acylation results, however, in a stabilization of the protein against heat-induced aggregation.

2S Albumins, Plant↗

Plant protein families and their relationships to food allergy.

The analysis of plant proteins has a long and distinguished history, with work dating back over 250 years. Much of the work has focused on seed proteins, which are important in animal nutrition and food processing. Early studies classified plant proteins into groups based on solubility ('Osborne fractions') or protein function. More recently, families have been defined based on stuctural and evolutionary relationships. One of the most widespread groups of plant proteins is the prolaminin superfamily, which comprises cereal seed storage proteins, a range of low-molecular-mass sulphur-rich proteins (many of which are located in seeds) and some cell wall glycoproteins. This superfamily includes several major types of plant allergen: non-specific lipid transfer proteins, cereal seed inhibitors of alpha-amylase and/or trypsin, and 2 S albumin storage proteins of dicotyledonous seeds.

Animals↗

Synthesis and processing of the plant protein thaumatin in yeast.

Various maturation forms of the plant protein thaumatin were expressed in yeast, using a promoter fragment of the glyceraldehyde- 3P -dehydrogenase (GAPDH) gene. Plasmids encoding preprothaumatin were shown to direct the synthesis of a processed form of the plant protein. The important role of signal sequences in the expression of the plant protein in yeast was indicated by the observation that plasmids encoding processed thaumatin forms were only poorly expressed, if at all. Nucleotide sequence analysis of the 843 nucleotide GAPDH promoter fragment revealed a characteristic structure with two regions of dyad symmetry containing translational starts of GAPDH and a putative 38 amino acid peptide. A promoter fragment from which the upstream region was deleted proved to be less efficient in thaumatin expression.

Base Sequence↗

Cholesterol metabolism in mature and immature rats fed animal and plant protein.

In two feeding experiments immature (180 g) and mature rats (370 g) were fed a semi-purified diet containing 20% of a protein source (casein, wheat gluten, soybean or potato protein) for 4 wk. Food supply was restricted to 15 g daily. As compared to casein, plant proteins induced significantly lower concentrations of plasma total cholesterol and high density lipoprotein (HDL) cholesterol. The plasma cholesterol increase associated with aging was not prevented by consumption of casein, soybean or potato protein, but wheat gluten seemed to be effective. Lecithin-cholesterol acyltransferase (LCAT) activity was not significantly different in rats of the same age fed different plant proteins, whereas the esterification rate was lower in rats fed casein. With aging the LCAT activity generally decreased. As compared to the casein groups, the rats fed plant proteins showed higher excretion of fecal neutral and acidic steroids. Among the groups fed plant proteins, the fecal output of steroids was variable. Significantly negative correlations were found between fecal total sterol excretion and plasma total cholesterol or HDL cholesterol, respectively. Plant proteins showed a faster migration rate in the stomach, whereas their migration and absorption were slower in the first half of the small intestine. A relation between nonabsorbed nitrogen-containing substances and sterol excretion was hypothesized.

Aging↗

Functional and Nutritional Potential of Chickpea Protein Hydrolysates: A Systematic Review and Plant-protein Network Analysis.

Chickpea is a protein-rich legume increasingly explored as a substrate for functional plant-based ingredients. Chickpea protein hydrolysates (CPHs) and chickpea-derived peptides (CPs), obtained through enzymatic hydrolysis or simulated gastrointestinal digestion, may provide technological and biological properties while supporting the valorization of chickpea fractions and by-products. This review integrates a network analysis of title-abstract terms from 5,728 unique Scopus and PubMed records on plant protein hydrolysates with a systematic review of 72 studies focused on CPH production, peptide characterization, bioactivity, and translational gaps. The evidence indicates that CPHs and CPs show promising antioxidant, antihypertensive, antidiabetic, anti-inflammatory, lipid-lowering, immunomodulatory, antimicrobial, and anticancer-related activities, mainly supported by biochemical assays, cell models, and animal studies. However, heterogeneous hydrolysis protocols, incomplete peptide characterization, inconsistent bioactivity methods, limited scale-up evidence, and the absence of human intervention trials restrict translation. Future studies should prioritize standardized protocols, mechanistic validation, bioavailability, sensory and regulatory assessment, food-matrix validation, and clinical trials.

Cicer↗

Isoprenylation of plant proteins in vivo. Isoprenylated proteins are abundant in the mitochondria and nuclei of spinach.

Protein isoprenylation in vivo is demonstrated using spinach seedlings labeled with [3H]mevalonate. This report provides evidence for the occurrence of a large number of isoprenylated proteins in plants. Seedlings, without roots, were labeled quantitatively through the cut stem. Mevinolin treatment of the seedlings resulted in increased incorporation of radiolabel into proteins. Approximately 30 labeled bands could be detected after autoradiography of SDS-polyacrylamide gel electrophoresis-separated polypeptides, ranging in molecular mass from 6 to 200 kDa. Methyl iodide hydrolysis resulted in the release of covalently bound farnesol, geranylgeraniol, phytol, and some unidentified isoprenoid compounds from mevalonate-labeled proteins. It was found that all cellular fractions contained some isoprenylated proteins, although most were located in the mitochondria and nuclei. Subfractionation of the nucleus revealed that the majority of isoprenylated proteins in this compartment were components of the nuclear matrix. The results demonstrate that in vivo labeling of a complex organism can be performed using a plant system in order to study protein isoprenylation and distribution of modified proteins in different cellular compartments.

Cell Nucleus↗

Identification of a 37 kDa plant protein that interacts with the turnip mosaic potyvirus capsid protein using anti-idiotypic-antibodies.

Experimental data are provided for the presence of a plant protein that interacts with the capsid protein (CP) of turnip mosaic potyvirus (TuMV). The receptor-like protein was identified by exploiting the molecular mimicry potential of anti-idiotypic antibodies. A single-chain Fv molecule derived from the monoclonal antibody 7A (Mab-7A), which recognizes the CP of TuMV, was produced in Escherichia coli and the recombinant protein was used to raise rabbit antibodies. The immune serum reacted with Mab-7A but not with a monoclonal antibody of the same isotype, indicating that anti-idiotypic antibodies were produced. These anti-idiotypic antibodies recognized a 37 kDa protein from Lactuca sativa. Complex formation between the anti-idiotypic antibodies and the plant protein was inhibited by the CP of TuMV which indicates that the plant protein interacts with the viral protein. The 37 kDa protein was localized in chloroplasts and was detected in other plant species.

Animals↗

Domains as functional building blocks of plant proteins.

Emerging evidence in eukaryotic systems suggests that many proteins of diverse cellular processes are made up of protein domains that are well defined in both sequence and structure. This article updates the identification of many 'classic' eukaryotic protein domains in various plant cellular processes, with particular emphasis on the non-catalytic categories. We discuss the importance of domains to plant-protein functions and cellular networking, and the emergence of plant-specific domains.

Amino Acid Sequence↗

Adsorption kinetics and rheological interfacial properties of plant proteins at the oil-water interface.

Adsorption and rheological properties of plant proteins were determined by means of the dynamic pendant drop technique. The plant protein properties were compared with the interfacial properties of gelatin, which is well-known for its surface-active properties and is commonly used in food and health products. The results showed that alpha gliadins (wheat proteins) and pea globulins have the highest surface active properties at the oil-water interface, even higher than gelatin at the same concentration (weight/volume). After a short time of adsorption, alpha gliadin interfacial behavior is characterized by a pronounced viscoelasticity, which was confirmed with time whereas pea protein interfacial behavior became elastic after a long initial adsorption period. Finally, the behavior of gelatin is very close to the alpha gliadin behavior for the short initial adsorption period, whereas it looks like the behavior of legume seed proteins for longer times of the adsorption kinetics. This study emphasizes the importance of the choice of the proteins and the emulsification time in the encapsulation process, according to the interfacial behavior.

Adsorption↗

PLANT PROTEIN SERINE/THREONINE KINASES: Classification and Functions.

The first plant protein kinase sequences were reported as recently as 1989, but by mid-1998 there were more than 500, including 175 in Arabidopsis thaliana alone. Despite this impressive pace of discovery, progress in understanding the detailed functions of protein kinases in plants has been slower. Protein serine/threonine kinases from A. thaliana can be divided into around a dozen major groups based on their sequence relationships. For each of these groups, studies on animal and fungal homologs are briefly reviewed, and direct studies of their physiological functions in plants are then discussed in more detail. The network of protein-serine/threonine kinases in plant cells appears to act as a "central processor unit" (cpu), accepting input information from receptors that sense environmental conditions, phytohormones, and other external factors, and converting it into appropriate outputs such as changes in metabolism, gene expression, and cell growth and division.

Journal Article↗