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Biomedical subjects

G A Strobel

Publications and source records attributed to G A Strobel.

At least 37 records · Page 2Linked to original sources
PubMed1980

Inverse relationship of protein concentration and binding activity of alpha-galactoside receptors from sugarcane membranes.

1. The binding activity of purified alpha-galactoside receptor proteins from a number of plant species decreases when the protein concentration is increased from 2 ng/ml to 100 micrograms/ml. 2. The apparent loss of binding activity at high protein concentrations corresonds to the formation of high molecular weight multimers. 3. Raffinose and melibiose cause a ligant-dependent increase in binding activity and a corresponding decrease in the relative abundance of multimers at any give protein concentration. 4. The self-inhibition of binding activity at high protein concentrations arises from a competition between ligant binding by oligomers and self-association of these oligomers into multimeric species which have little or no binding acitivity.

Binding, Competitive↗
PubMed1980

Some synthetic phytotoxins structurally related to rhynchosporoside.

The (2-O)alpha-d-glucopyranoside of 1,2-propanediol and [U-(14)C]glucose were used as substrates in a reaction with almond beta-glucosidase, which resulted in the production of some (2-O)alpha-d-oligoglucosides of 1,2-propanediol. As its substrate, the beta-glucosidase preferred the glucoside isomer that rotates plane-polarized light to the right. Some of the glucosides produced in the enzymic reaction mixture possessed host selective toxin activity. It appears that the biological activity of the toxin is not dependent on the nature of the glycosidic linkage with the aglycone.

Journal Article↗
PubMed1979

The relationship between membrane ATPase activity in sugarcane and heat-induced resistance to helminthosporoside.

1. Heating of susceptible sugarcane leaves (4 h at 35 degrees C) renders them resistant, for 24 h, to the effects of helminthosporoside. Membrane ATPase activity is reduced by 50% as a result of the heat treatment. When the leaves again become susceptible (after 24 h), membrane. ATPase activity is fully restored. 2. Inhibitors of membrane ATPase activity protect susceptible leaves from the effects of helminthosporoside (KF, EDTA, and octylguanidine). 3. Helminthosporoside activates (30%) membrane ATPase in microsomes from susceptible, but not heat-treated (resistant) leaves. Once heat-treated leaves again become susceptible, helminthosporoside activation of membrane ATPase activity resumes. 4. A plot of the production of helminthosporoside-induced symptoms, and membrane ATPase activity as a function of the reciprocal of the absolute temperature reveals that both have sharp breaks at 32 degrees C. 5. Protoplasts of susceptible cane are rendered insensitivity to the effects of the toxin in a medium deficient in K+ and Mg2+. When these ions are added, cell sensitivity to the toxin is restored. Since K+ uptake in plants is mediated by membrane ATPase, a connection with this enzyme activity can be made to cell sensitivity to the toxin.

Adenosine Triphosphatases↗
PubMed1978

Serinol phosphate as an intermediate in serinol formation in sugarcane.

A novel compound, serinol phosphate, was identified in sugarcane (Saccharum officinarum) clone 51NG97. It was produced by an enzyme-mediated transamination of dihydroxyacetone phosphate with either alanine, glutamate, aspartate, or glutamine serving equally well as an amino donor. Some detectable phosphatase activity was present in crude leaf enzyme preparation that hydrolyzed serinol phosphate. A proposal for a pathway of the biosynthesis of serinol in sugarcane was formulated.Serinol can serve as an "activator" of toxin production in attenuated cultures of the sugarcane pathogen Helminthosporium sacchari and it is present in susceptible clone 51NG97. Resistant clone H50-7209 does not possess serinol and likewise no dihydroxyacetone phosphate transaminase activity could be demonstrated in enzyme preparations of this clone. The concept of toxin activation in attenuated fungus cultures is briefly discussed relative to disease resistance and susceptibility.

Journal Article↗
PubMed1977

Assay for Helminthosporium maydis Toxin-binding Activity in Plants.

A relatively rapid and sensitive assay is described for assessing the binding of Helminthosporium maydis Race T(14) C-toxins I and II to plant components. The technique is a modification of the one of Haddad and Birge (J. Biol. Chem. 250: 299-303, 1975), and utilizes dextran-coated charcoal as an adsorbent for the unreacted toxin and employs a Millipore filter to isolate the protein-toxin complex.Extracts from susceptible corn line W64A Tms possess a protein primarily localized in the cytosol which is relatively heat-insensitive, ficin- and papain-sensitive, and binds toxins I and II at half-saturation in the order of 0.1 mm. The toxin-binding activities of the extracts of various corn lines and other species are not correlated to resistance or susceptibility to H. maydis Race T, nor to sensitivity to the toxins. These findings are discussed relative to the function of the binding protein and cellular sensitivity to the toxins.

Journal Article↗
PubMed1977

Bacterial phytotoxins.

Representatives of all of the major genera of plant disease-causing bacteria have been shown to produce one or more phytotoxins. Toxicological studies on the bacterial diseases of the major food crops have not been extensive. Bacterial phytotoxins belong to a number of classes of organic substances, including peptide, derivatized amino acid, polysaccharide, and glycopeptide. The mechanism of action of these compounds is largely unknown, as is their origin and importance in the disease syndrome. Nevertheless, some progress has been made in these areas in isolated cases. There is a tremendous potential in the future for studies on the bacterial phytotoxins.

Bacterial Proteins↗
PubMed1976

Chemotaxis of Rhizobium spp. to Plant Root Exudates.

Rhizobium spp. show chemotaxis to plant root exudates. Both legumes and non-legume root exudates attract the different rhizobia studied. However, the bacteria show a differential response in that they are attracted to the root exudates of some plants and show no attraction toward others. An example of negative chemotaxis was also observed. The trefoil strain of Rhizobium shows chemotaxis which is qualitatively different from that observed in other bacteria in that simple sugars, di-and trisaccharides, dextrans, and amino acids do not attract this bacterium.

Journal Article↗
PubMed1975

Deficiency of toxin-binding protein activity in mutants of sugarcane clone H54-775 as it relates to disease resistance.

Three mutants selected from a population of sugarcane clone H54-775 that had been irradiated with 3 kR gamma-radiation all lacked toxin-binding protein activity. This activity previously had been shown to be essential for eye spot disease susceptibility and was demonstrated in the susceptible parent clone H54-775. In one mutant, the biochemical, immunochemical, and electrophoretic mobilities of the toxin-binding protein were all modified.

Carrier Proteins↗
PubMed1975

Isolation and Characterization of Stemphylin, a Chromone Glucoside from Stemphylium botryosum.

A phytotoxic compound was isolated from a liquid culture medium of Stemphylium botryosum, a pathogen of lettuce. The toxin is an amorphous yellow solid with absorbance maxima at 218, 268, and 427.5 nm and exhibits a bathochromic shift in alkaline pH. It has a molecular weight of 370 and an empirical formula of C(17)H(22)O(9). Glucose and aromatic pigments are detected after acid hydrolysis. Based on its spectral and chemical properties, the proposed structure of the toxin is 3-hydroxy- 2,2-dimethyl-5-alpha-d-glucopyranoside-2,3-dihydrochromone, and it has been given the trivial name stemphylin. A linear relationship exists between lesion area and amount of toxin applied to a young lettuce leaf. The relationship between toxin production and the development of disease symptoms is discussed.

Journal Article↗
PubMed1975

The Toxins of Helminthosporium maydis (Race T) : A Colorimetric Determination of the Toxins, Their Appearance in Culture and in Infected Plants.

Host-specific toxins produced by Helminthosporium maydis, race T, are measured quantitatively by a chemical assay procedure involving reaction of the toxins with a sulfuric acidacetic anhydride reagent and measurement of the absorbance of the product at 330 nm. The assay was shown to measure total toxin concentrations after only limited fractionation of the culture medium. Using the assay it was possible to show that the highest amount of toxin per gram of fungus mycelium occurs early in the growth cycle of H. maydis. Toxins I, II, and V are the predominant toxins at these early times both in culture and in infected corn and wheat varieties. Some chromatographic and spectral properties of toxin V, a previously unreported toxin, are described. Since toxin V appears in culture prior to toxins I, II, III and IV, a precursor-product relationship can be suggested.

Journal Article↗
PubMed1974

The toxin-binding protein of sugarcane, its role in the plant and in disease development.

The toxin-binding protein of sugarcane susceptible to eyespot disease also possesses raffinose-binding activity. The K(m)'s for binding are: helminthosporoside (toxin) 6.8 x 10(-5) M, raffinose 2.5 x 10(-5) M, and melibiose 2.6 x 10(-5) M. Evidence obtained by administering [(14)C]raffinose to sugarcane protoplasts suggests that this protein participates in alpha-galactoside transport. Cells from a resistant clone of sugarcane do not possess an active-binding protein, and likewise, do not actively take up raffinose. Interestingly, the K(+), Mg(++) ATPase (ATP phosphohydrolase, EC 3.6.1.3.) on the plasma membrane of the susceptible sugarcane is 30% activated by the toxin at 3 mM. In addition, toxin-treated tissue slices show a rapid uptake of (86)Rb(+)-K(+) which is in agreement with the toxin activation of the membrane K(+), Mg(++) ATPase. Since the ATPase does not directly interact with the toxin, the activation effect occurs by means of the toxin-binding protein. Membrane proteins may be influenced by the toxin-binding protein acting by one of several different mechanisms.

Journal Article↗
PubMed1974

Evidence for the presence of the toxin-binding protein on the plasma membrane of sugarcane cells.

Helminthosporoside is a host-specific toxin produced by Helminthosporium sacchari, both in culture and in infected sugarcane tissue. The susceptibility of any given clone of sugarcane to disease is invariably associated with the presence of a toxin-binding protein. This report presents evidence for the presence of the toxin-binding protein on the plasma membrane of the plant cell. This evidence includes, among others: (1) The protection of susceptible plant tissues by prior treatment with antiserum to the binding protein, (2) the successful pyridoxylation and reduction of the binding protein in vivo followed by its isolation, (3) the reaction of sugarcane cells and free protoplasts with [(3)H]antiserum prepared against the binding protein, and (4) the agglutination of sugarcane protoplast preparations with antiserum to the binding protein.

Binding Sites↗
PubMed1974

Isolation and Partial Characterization of Four Host-specific Toxins of Helminthosporium maydis (Race T).

Helminthosporium maydis, race T, produces four host-specific toxins in culture. These have been designated toxins I, II, III, and IV. A method for isolation and purification of the four toxins is presented, and the criteria of purity of preparations of toxins I, II, and III are given. Toxins I and II are chemically similar and yield the same molecular ion when subjected to mass spectrometry, while toxin III appears to be a glycoside of a compound related to toxins I and II. Toxins I, II, and III can be biologically derived from (14)C-mevalonic acid or (14)C-acetate, permitting preparation of (14)C-labeled toxins. Some chemical, spectral, and chromatographic properties of toxins I, II, and III are presented, and these data are discussed relative to the possible structure of the three compounds. In addition, four host-specific toxins have been isolated from corn infected with H. maydis (race T). These toxins are recovered in the same fractions as toxins I, II, III, and IV using the isolation procedure described here. Three of the toxins isolated from infected corn cannot be distinguished from toxins I, II, and III on the basis of infrared spectra or chromatographic mobility.

Journal Article↗
PubMed1974

Photosynthesis in the Higher Plant, Vicia faba: III. Serine, a Precursor of the Tricarboxylic Acid Cycle.

Evidence is presented to support the hypothesis that serine, rather than 3-phosphoglycerate of the Calvin cycle, is a precursor of the tricarboxylic acid cycle during photosynthesis by the higher plant, Vicia faba. Identification of the serine intermediate is based upon a unique C(1) > C(2) > C(3) isotope distribution for that metabolite following the fixation of (14)CO(2). This labeling pattern, while incompatible with an origin either in the Calvin cycle or the glycolate pathway, satisfies a critical criterion for the 3-carbon precursor of the anomalously labeled organic acids. The predominant carboxyl carbon atom labeling of serine reflects either a mixing of two pools of that metabolite, ie., C(1) = C(2) > C(3) and C(1) > C(2) = C(3), or a higher order of complexity in its synthesis. An anomalous C(1) = C(2) > C(3) < C(4) distribution for aspartate, however, suggests an origin by the carboxylation of a 3-carbon intermediate related to serine which has a C(1) = C(2) > C(3) distribution. The latter distribution has been proposed for the serine intermediate of the postulated formate pathway. This pathway is described by the generalized metabolic sequence: CO(2) --> formate --> serine --> organic acids. Corresponding carbon atom distributions for citrate (C(1) > C(2)), aspartate (C(2) > C(3)), and serine (C(2) > C(3)) belie a precursor-product relationship with alanine (C(2) = C(3)), which is a molecular parameter of the Calvin cycle product, 3-phosphoglycerate.

Journal Article↗
PubMed1973

Biochemical basis of the resistance of sugarcane to eyespot disease.

Helminthosporoside is the host-specific toxin produced by Helminthosporium sacchari, the organism causing eyespot disease on sugarcane. Clones of sugarcane susceptible to the toxin posses a membrane protein that binds the toxin. Membranes of resistant clones do not bind the toxin. In this study, a binding protein from a susceptible clone was compared with its counterpart from a resistant clone. The protein from the resistant clone did not bind the toxin unless it was first treated with mild detergent. The two proteins are antigenically identical, have the same molecular weight, and each contains four subunits. They differ slightly in their electrophoretic mobility and vary with respect to four different aminoacid residues. The basis of resistance of clone H50-7209 to eyespot disease is directly associated with the structurally altered membrane-binding protein.

Journal Article↗