Correlation between Protein Body Formation and Storage Protein Accumulation in Soybean Cotyledons

At 20 days after flowering (DAF), the 7S α' and α subunits began to accumulate. At 25 DAF, the 7Sβ, l1SA and llSB subunits appeared. Five days later, the 11SA-4 subunit was present During the period of 25–55DAF, the storage protein content continued to increase. From 55 to 63 DAF, there was a decrease in the synthetic rate of the storage proteins. Comparing these results with the two paths of protein body formation reported previously, we draw the conclusion that the protein bodies developed from vacuoles contained not only the 7S bm also the lis proteins in soybean cotyledon cells.     

Free Amino Acid and Storage Protein Composition of Soybean Fruit Explants and Isolated Cotyledons Cultured with and without Methionine

Thein vitroculture of immature soybean cotyledons (in direct contact with the medium) and immature fruit explants (stem dipping into the medium) on a defined medium containing glutamine and sulphate as sole sources of N and S for 7 d led to rates of growth and reserve protein accumulation close to, or greater than, those occurringin situ. Supplementation of the medium with 8.4 mMmethionine had little effect on growth and protein accumulation of the cotyledons in the explant system, but did result in significant increases in the isolated cotyledon system. Methionine suppressed the synthesis of the 7S β-subunit in both systems. The free amino pool of the cotyledons increased more than three-fold when methionine was present in the explant medium. In the isolated cotyledon system, the basal medium alone caused a large increase (over 30-fold) in the free amino acid fraction, but methionine resulted in an even greater increase (over 50-fold). In both systems the expansion involved a very large increase in the methionine pool, but many other amino acids also showed large increases. Specific effects of methionine on individual amino acids were more clear in the explant system, where its presence resulted in marked increases in serine, alanine and asparagine. The data show that an abnormal situation arises on feeding with methionine, a fact to be considered before attributing effects on growth and protein synthesis directly to methionine.     

Absence of α-Ketoglutarate Dehydrogenase Activity and Presence of CO2-Fixing Activity in Plasmodium falciparum Grown In Vitro in Human Erythrocytes1

Plasmodium falciparum-infected human erythrocytes grown in vitro do not release ¹⁴CO₂, when incubated in the presence of [1-¹⁴C]glutamate, despite the presence of glutamate dehydrogenase, implying the absence of α-ketoglutarate dehydrogenase activity and the lack of functional tricarboxylic acid cycle in the human malaria parasite. Cultures incubated with [¹⁴C]bicarbonate, however, fix CO₂ into acid-stable metabolites; CO₂ fixation proceeds linearly for up to two hours after an initial brief lag and may contribute appreciably to the metabolism of the parasite.     

Tau融合蛋白及其缺失突变体与朊蛋白的体外作用分析

在部分朊病毒病（prion diseases）中,高度磷酸化的微管相关蛋白tau与朊蛋白(prion protein,PrP)发生共定位,tau蛋白可能在朊病毒病的病理机制中有重要作用. 本室已经证明二者可以发生分子间相互作用,本文进一步分析了tau蛋白与prion的体外相互作用及作用位点. 利用RT-PCR方法从人源细胞系SHSY5Y cDNA中扩增出微管相关蛋白tau全长cDNA序列,克隆至质粒pGEX-2T载体,在大肠杆菌中诱导表达融合蛋白GST-tau. 利用GST pull-down及免疫共沉淀方法检测全长tau蛋白与PrP23-231的分子间相互作用. 进一步表达tau 蛋白的各种缺失突变体,确定tau蛋白与PrP蛋白的相互作用位点. 结果表明,所表达的全长tau蛋白及各种缺失突变体均为可溶性蛋白,Western印迹结果显示,各种蛋白均能很好的被tau蛋白单抗识别. GST pull-down和免疫共沉淀实验均显示,原核表达的全长tau蛋白可与全长的PrP蛋白在体外发生相互作用,并确定相互作用位点位于tau蛋白的N端序列及中段的重复区. 上述结果为研究tau蛋白与PrP的相互作用在朊病毒病的发病机制中的意义提供了一定的理论基础.     

Synthesis of Biologically Active Lipids by the Fungus Mucor lusitanicus 306D Grown on Media with Various Composition

Growth and lipogenesis of the fungusMucor lusitanicus306D, producing -linoleic acid, was studied under various conditions of nitrogen and carbon nutrition. Media containing food-industry wastes, such as maize extract, molasses, and protein hydrolysate, were used. The content of -linoleic acid was higher when carbohydrates (glucose and molasses) were used as carbon sources and urea was used as a nitrogen source. At a high glucose concentration (100 g/l), fed batch cultivation ensured high contents of -linoleic acid in lipids (1 g/l). After extraction of lipids, the fungus biomass was 42% protein, containing all essential amino acids. A defatted biomass was shown to be effectively assimilated by minks.     

Growth Response to Cyanide by Plants Grown in the Presence or Absence of Iron

Seedlings of Phaseolux vulgaris were grown in media with and without iron. Growth was measured in terms of leaf length and fresh weight increase. Cyanide at & concentration of 0.05 mM was found to inhibit severely plants growing in complete media but failed to inhibit growth to (he same extent in those plants grown in media lacking iron. It was established that this result was obtained whether the plants were grown in an unchanged medium or if the growth medium was replaced at intervals. A number of suggestions were made in an attempt to account for this anomalous behavior.     

A Comparison of Soybean Globulins and the Protein Bodies in the Protein Composition

The protein compositions between soybean globulins and the protein bodies were compared by gel filtration with Sephadex G-200, sedimentation analyses and disc isoelectric focusing.

From the results of the three comparisons, it was difficult to find an essential difference in the protein compositions of the both. And, the 7S and the 11S globulins were the main components in the both. This fact was more strongly suggested that these globulins were the typical reserve proteins.     

Thermal Inactivation of Susceptible and Multiantimicrobial-Resistant Salmonella Strains Grown in the Absence or Presence of Glucose

The heat resistance of susceptible and multiantimicrobial-resistant Salmonella strains grown to stationary phase in glucose-free tryptic soy broth supplemented with 0.6% yeast extract (TSBYE−G; nonadapted), in regular (0.25% glucose) TSBYE, or in TSBYE−G with 1.00% added glucose (TSBYE+G; acid adapted) was determined at 55, 57, 59, and 61°C. Cultures were heated in sterile 0.1% buffered peptone water (50 μl) in heat-sealed capillary tubes immersed in a thermostatically controlled circulating-water bath. Decimal reduction times (D values) were calculated from survival curves having r² values of >0.90 as a means of comparing thermal tolerance among variables. D_59°C values increased (P < 0.05) from 0.50 to 0.58 to 0.66 min for TSBYE−G, TSBYE, and TSBYE+G cultures, respectively. D_61°C values of antimicrobial-susceptible Salmonella strains increased (P < 0.05) from 0.14 to 0.19 as the glucose concentration increased from 0.00 to 1.00%, respectively, while D_61°C values of multiantimicrobial-resistant Salmonella strains did not differ (P > 0.05) between TSBYE−G and TSBYE+G cultures. When averaged across glucose levels and temperatures, there were no differences (P > 0.05) between the D values of susceptible and multiantimicrobial-resistant inocula. Collectively, D values ranged from 4.23 to 5.39, 1.47 to 1.81, 0.50 to 0.66, and 0.16 to 0.20 min for Salmonella strains inactivated at 55, 57, 59, and 61°C, respectively. z_D values were 1.20, 1.48, and 1.49°C for Salmonella strains grown in TSBYE+G, TSBYE, and TSBYE−G, respectively, while the corresponding activation energies of inactivation were 497, 493, and 494 kJ/mol. Study results suggested a cross-protective effect of acid adaptation on thermal inactivation but no association between antimicrobial susceptibility and the ability of salmonellae to survive heat stress.     

不同成熟度花生胚萌发时子叶中贮藏蛋白质的降解

花生(Arachis hypogaea L.)汕油71果针入土20d(20 DAP)的种子剥去种皮后,10％的胚可以萌发,至40 DAP发芽率达98％。不同发育时期的花生胚萌发 10d后子叶盐溶蛋白质和花生球蛋白降解表明,20和32 DAP胚萌发后,子叶中这些蛋白质只有部分降解。随着胚成熟度增加,子叶中降解这些蛋白质的能力不断提高。20～40 DAP胚萌发4d时,子叶的BAPAase和GHE活性较低。50～80DAP胚萌发 4d,子叶中上述两种酶均显示较高的活性。     

Phytochrome Responses to End-of-Day Irradiations in Light-grown Corn Grown in the Presence and Absence of Sandoz 9789

Corn seedlings were grown in white light in the absence and presence of the chlorosis-inducing herbicide San 9789. The resulting green and achlorophyllous seedlings were used to investigate phytochrome-mediated responses to end-of-day far red irradiation and reversal of these responses by subsequent red irradiation. Mesocotyl and coleoptile elongation increased in response to end-of-day far red irradiation, whereas the anthocyanin content of the coleoptiles was decreased. All three responses were reversible by red irradiation following the far red. Dose-response curves for far red induction and red reversal of these responses did not differ significantly for plants grown in the presence or absence of San 9789. Thus, San 9789 appears to affect neither phytochrome itself nor the response system involved. Chlorophyll screening likewise does not affect phytochrome relationships for these responses.     

In Vitro Study of Mitochondrial Protein Synthesis during Mitochondrial Biogenesis in Excised Plant Storage Tissue

Mitochondrial biogenesis was induced in Jerusalem artichoke (Helianthus tuberosus) tuber by aging tissue discs in distilled water for up to 26 hours. Changes in the purified mitochondrial fraction during aging included an increase in both protein content and specific respiratory activity. Using intact isolated mitochondria, conditions were optimized for incorporation of radioactive amino acid into protein. Incorporation was dependent upon the supply of an oxidizable substrate or an external ATP-generating system and showed characteristic sensitivity to inhibitors of protein synthesis. Aging of the tissue resulted in a 3-fold increase in the rate of in vitro incorporation of [³⁵S]methionine into mitochondrial protein. An analysis of the free amino acid pool in the mitochondrial fraction showed that the decrease in methionine level during aging of intact tissue was sufficient to account for the increased rate of protein labeling. The activation of mitochondrial biogenesis which occurs after slicing is not dependent on an increase in the capacity of mitochondria to synthesize protein as assayed in vitro.     

Emergence of Proteases in Germinating Cucumber Cotyledons and Their Roles in the Two-Step Degradation of Storage Protein

The degradation of storage protein in germinating cucumber seedswas shown to proceed via two distinct steps. First, severalproteases with acidic isoelectric points (pIs) were involvedin solubilization and partial degradation of 11S globulin. Treatmentof seedlings with cycloheximide inhibited this step and theexpression of these proteases. Thus, the first step appearedto be governed by these proteases, which were synthesized denovo after imbibition. The first step was observed in dark-growncotyledons, but the complete degradation of 11S globulin didnot occur in the absence of illumination. An additional protease,with a pI of 4.5, was induced by illumination, and it was involvedin the further cleavage of the partially degraded products ofIIS globulin. Thus, the complete degradation of the storageprotein proceeded via a two-step process in illuminated germinatingseedlings. Light is needed to induce the second step in thedegradation of 11S globulin that supplies the nitrogen requiredfor development of the photosynthetic apparatus in the greeningcotyledon. (Received November 9, 1995; Accepted January 31, 1996)     

Tetrahymena Thermophila: Growth In Synthetic Nutrient Medium In the Presence and Absence of Glucose

ABSTRACT This report contains the newest directions for preparation of the synthetic nutrient medium for some Tetrahymena species that do not require lipids. In the standard medium T. thermophila. strains SB 210 and 281, multiply at 37°C with doubling times of around 2 h and at 26°C around 5 h. We have established multiplication rates as functions of variations in the composition of the medium. In media in which all components are present at one-third of the normal concentrations and only the essential amino acids are included, growth and multiplication become sharply dependent on glucose in strain SB 281. Such media may be used for selection and enrichment of certain specified cell lines.     

Lipid Composition of the Yeastlike and Mycelial Mucor hiemalis Cells Grown in the Presence of 4-Chloroaniline

The fungus Mucor hiemalis F-1156, which is commonly thought to be monomorphic, produced two types of cells, yeastlike and mycelial, during growth in a medium containing 4-chloroaniline. Among the polar lipids of yeastlike cells, diphosphatidylglycerol was dominant, while phosphatidylcholine and phosphatidylethanolamine were present in minor amounts. Conversely, mycelial cells mainly contained phosphatidylcholine and phosphatidylethanolamine, whereas the content of diphosphatidylglycerol was low. The neutral lipids of yeastlike cells were dominated by diacylglycerides, sterols, and fatty acids. The content of triacylglycerides and sterol esters was low. Yeastlike cells contained higher amounts of saturated fatty acids and lower amounts of unsaturated fatty acids than the mycelium. The content of stearic acid in the fatty acids of the mycelium grown in the presence of 4-chloroaniline was as high as 25.3–29.9%.     

Location and State of Methionine Residues in a Papain-synthesized Plastein from a Mixture of Soybean Protein Hydrolysate and l-Methionine Ethyl Ester

With the aid of papain, a plastein was synthesized from a 1 : 10 mixture of l-methionine ethyl ester and a peptic hydrolysate of soybean protein. Dialysis of the whole reaction-product yielded a methionine-incorporated plastein (Met-plastein) as the nondialyzable fraction, its yield being 78.2% on a dry-matter basis, of the whole reaction-product. Methionine content in this Met-plastein was 7.22% on a weight basis, while its content in the material hydrolysate was only 1.25%. Carboxypeptidase A treatment of Met-plastein liberated methionine at an outstandingly rapid rate. A similar, but not so outstanding, rate was observed for the methionine liberation from Met-plastein by treatment with leucine aminopeptidase. Methyl isothiocyanate treatment and subsequent cyclization yielded a mixture of methylthiohydantoins from Met-plastein. Gas chromatographic analysis of this mixture after trimethylsilylation showed a result that methionine occupied 33.2%, on a molar basis, of the total N-terminal amino acids. Lithium borohydride reduction and 6 n hydrochloric, acid hydrolysis of Met-plastein produced monomeric aminois, and their 2,4-dinitrophenylation followed by thin-layer chromatography gave a result that methionine occupied 84.9%, on a molar basis, of the total C-terminal amino acids; the residues amounting to 14.4% of the C-terminal methionine residues remained as an ethyl eater form. The selective degradation probe employing cyanogen bromide to generate free homoserine disclosed that the occurrence of the polymeric methionine-methionine sequence was little if any in Met-plastein. Based on the above experiments as well as an evaluation of the esterase activity against l-methionine ethyl ester, a possible mechanism was discussed of the papain-catalyzed synthesis of plastein in a system containing such an ester.     

Farnesol Concentrations Required To Block Germ Tube Formation in Candida albicans in the Presence and Absence of Serum

Concentrations of (E,E)-farnesol needed to inhibit germ tube formation were determined for Candida albicans strains A72 and SC5314 by using six different conditions known to trigger germination. For defined media, 1 to 2 μM farnesol was sufficient. However, with serum at 2 to 20%, up to 250 μM farnesol was required. Farnesol blocked germ tube formation but did not block elongation of existing germ tubes.     

Storage Protein Synthesis in Maize: III. Developmental Changes in Membrane-bound Polyribosome Composition and in Vitro Protein Synthesis of Normal and Opaque-2 Maize

Zein synthesis accompanied an increase in large polyribosomes of maize (Zea mays) endosperm cells. The two classes of polyribosomes (free and membrane-bound) had dissimilar size class distributions. Membrane-bound polyribosomes were predominantly large size classes, which were not found in free polyribosomes. The ratio of large membrane-bound polysomes to total membrane-bound polysomes was highest when zein was being synthesized. Appearance of the large polysomes correlated with the onset of zein accumulation in vivo. These large size classes were nearly absent in the opaque-2 mutant at all stages of endosperm development. Similarly, rRNA content was reduced in the mutant from that in normal endosperm development. These differences were associated with reduced in vitro synthesis and in vivo accumulation of zein.