Crystallographic studies of a calcium binding lysozyme from equine milk at 2.5 A resolution

The crystal structure of a calcium binding equine lysozyme has been determined at 2.5 A resolution by means of molecular replacement. The energy minimized equine lysozyme as the starting model, was refined with the molecular dynamics program, X-PLOR, and the R factor of the current model was found to be 24% without any water molecules. The conformation of the calcium binding loop is similar to that of alpha-lactalbumin. The profiles of backbone atomic displacements throughout the lysozyme and alpha-lactalbumin superfamilies are comparable as well as their homologous tertiary structures.

Substantial increase of the inhibitory activity of Mirabilis antiviral protein by an elimination of the disulfide bond with genetic engineering

Mirabilis antiviral protein (MAP) is a rigid, heat-stable protein composed of 250 amino acids with an intramolecular disulfide bond. MAP inhibits the in vitro protein synthesis of rabbit reticulocyte with approximately one-thirtieth the activity of the ricin A chain, a homologous protein with no such bond (Habuka, N., Murakami, Y., Noma, M., Kudo, T., and Horikoshi, K. (1989) J. Biol. Chem. 264, 6629-6637; Habuka, N., Akiyama, K., Tsuge, H., Miyano, M., Matsumoto, T., and Noma, M. (1990) J. Biol. Chem. 265, 10988-10992). The bond is presumed to induce some structural perturbation that alters the mode of interaction with the substrate ribosome and thus lowers the activity. To confirm this hypothesis, a mutant MAP gene in which the codons of both cysteines were replaced by those of serines was constructed and expressed in Escherichia coli, and its product (C36/22OS) was purified. In a sodium dodecyl sulfate-polyacrylamide gel electrophoresis, C36/220S showed the same mobility as that of MAP reduced by 2-mercaptoethanol, whereas nonreduced MAP showed faster migration. The inhibitory activity of C36/220S was approximately 22 times higher than that of native MAP, that is the mutant had an IC50 of 0.16 nM for the protein synthesis of the rabbit reticulocyte system, whereas the native MAP had an IC50 of 3.5 nM. The results indicate that the activity of MAP is increased by the elimination of the disulfide bond, and this supports the hypothesis.

Molecular cloning and expression of platelet-activating factor receptor from human leukocytes

The cDNA for a platelet-activating factor (PAF) receptor was cloned from a human leukocyte cDNA library using a 0.8-kilobase pair fragment of the guinea pig lung PAF receptor cDNA (Honda, Z., Nakamura, M., Miki, I., Minami, M., Watanabe, T., Seyama, Y., Okado, H., Toh, H., Ito, K., Miyamoto, T., and Shimizu, T. (1991) Nature 349, 342-346). The cDNA (1.8-kilobase pairs) had an open reading frame encoding 342 amino acid residues with a calculated Mr of 39,203. The clone was shown to code for a PAF receptor based on the following criteria: 1) the amino acid sequence possesses seven putative membrane spanning domains with 83% identity to the guinea pig lung PAF receptor, 2) Xenopus laevis oocytes injected with the transcript of the clone showed an electrophysiological response to PAF, and 3) COS-7 cells expressing the encoded receptor showed ligand binding with the pharmacological properties of the PAF receptor. Activation of the PAF receptor yielded inositol 1,4,5-trisphosphate production in both COS-7 cells and oocytes, and guanosine 5'-O-(2-thio)bisphosphate injection into the oocytes inhibited PAF-induced Cl- current, providing an evidence that PAF stimulates phosphoinositide turnover via G-protein(s). PAF receptor mRNA was abundant in leukocytes and less so in an undifferentiated human eosinophilic cell line (EoL-1 cells) or human erythroleukemia cells (HEL cells). The production of the mRNA was prominently increased when EoL-1 cells were treated with granulocyte macrophage colony stimulating factor, interleukin-5, and n-butyrate.

Escherichia coli ribosome is inactivated by Mirabilis antiviral protein which cleaves the N-glycosidic bond at A2660 of 23 S ribosomal RNA

Ribosome-inactivating proteins (RIPs) are known to inactivate eukaryotic ribosomes, which results in the inhibition of protein synthesis, but there has been no evidence that they inactivate the ribosomes of Escherichia coli. Recently, Mirabilis antiviral protein (MAP), a RIP, has been shown to inhibit the protein synthesis of E. coli as well as eukaryotes. To elucidate its mechanism, E. coli ribosomes treated with MAP were analyzed by polyacrylamide/agarose composite gel electrophoresis and RNA sequencing using reverse transcriptase with DNA primer. The 23 S rRNAs, with an A260 value for ribosomes of 15, were completely cleaved in vitro by a 30 minute treatment with MAP at a concentration of 100 nM at 37 degrees C and a subsequent treatment with aniline. However, they were not affected by ricin A-chain under the same conditions. The primer extension of DNA polymerization stopped before A2660 of 23 S rRNA in RNA sequencing. Furthermore, both 16 S and 23 S rRNAs were cleaved by the MAP and aniline treatments when naked E. coli rRNAs were used as substrates, and the primer extension stopped before bases A2660 and A1014, respectively, in RNA sequencing. As the A2660 region has been shown to interact with the elongation factors EF-Tu and EF-G these results indicate that MAP cleaves the N-glycosidic bond at A2660 in E. coli 23 S RNA resulting in the inactivation of the ribosome.

Inhibitory effects of 3-nitro-2,4,6-trihydroxybenzamides on Epstein-Barr virus early antigen induction

Inhibitory effects of a series of 3-nitro-2,4,6-trihydroxybenzamides on Epstein-Barr virus early antigen (EBV-EA) induction were examined using Raji cells. Some of the tested compounds showed highly inhibitory activity, the N-octyl amide derivative being the most active among them. These results suggest the possibility that 3-nitro-2,4,6-trihydroxybenzamides might be listed as novel inhibitors of tumor promotion.

A structural study of calcium-binding equine lysozyme by two-dimensional 1H-NMR

Since 1H-NMR spectra of the calcium bound form (holo) and the calcium free form (apo) of equine lysozyme have an overall similarity, the folded structure of apo equine lysozyme seems to be similar to the holo structure at 25 degrees C and pH 7.0, even at low ionic strengths except for subtle conformational change. However, calcium titration experiments showed that a number of resonances change by a slow exchange process. The changes saturated at one calcium ion per one lysozyme molecule, and no more change was observed by further addition of calcium ions. This shows that just one calcium ion binds to equine lysozyme. To make assignments for these changed proton resonances, two-dimensional 1H-NMR studies, correlated spectroscopy (COSY), two-dimensional homonuclear Hartmann-Hahn spectroscopy (HOHAHA) and nuclear Overhauser effect spectroscopy (NOESY) were carried out. A structural model of equine lysozyme based on the crystal structure of human lysozyme was estimated and used to assign some resonances in the aromatic and beta-sheet regions. It was possible to use some proton signals as a probe to determine the specific conformational change induced by calcium ions. The calcium binding constant KCa was estimated from calcium titration experiments in which changes in the proton signal were monitored. The log KCa value was found to be on the order of 6-7, which is in agreement with the calcium binding constant determined by fluorescence probes. This means that the protons are affected by specific calcium binding.

Expression and secretion of Mirabilis antiviral protein in Escherichia coli and its inhibition of in vitro eukaryotic and prokaryotic protein synthesis

Mirabilis antiviral protein (MAP), a ribosome-inactivating protein, exhibits inhibitory effects on both plant virus infection and protein synthesis. To study these functions by site-specific mutagenesis, the total synthetic gene of MAP was constructed and expressed in Escherichia coli. However, the growth of the host was inhibited by the products, and the yield of MAP was very low. To improve the system for expressing MAP, an expression vector, pSH7, was constructed. This vector is based on the high copy number plasmid pUC19 and includes PL promoter and temperature-sensitive cI857 repressor. The plasmid also contains the ompA signal sequence and the total synthetic MAP gene. The MAP gene was expressed and its product was secreted into the culture medium after E. coli transformants were cultivated at 30 degrees C and the temperature was raised to 42 degrees C. The secreted MAP was then purified and characterized. This protein was identical to native MAP as determined by its mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the amino acid sequence at the NH2 terminus, and its inhibitory effect on in vitro protein synthesis. MAP was found to inhibit the in vitro protein synthesis of rabbit reticulocyte and wheat germ. It further showed an IC50 concentration of approximately 200 nM in an E. coli in vitro translation system in contrast to ricin A-chain, a well known ribosome-inactivating protein.

Expression of a cDNA encoding human 5-lipoxygenase under control of the STA1 promoter in Saccharomyces cerevisiae

A yeast-expression vector utilizing the STA1 promoter was constructed, and shown to be useful for the expression of a heterologous gene. A cDNA, encoding human 5-lipoxygenase (5LO), was inserted into the vector and expressed in Saccharomyces cerevisiae. The enzyme (yh5LO) produced in the transformant was purified to homogeneity from the cellular soluble fraction. The purified enzyme showed both 5LO and leukotriene A4 synthase activities, which were stimulated by Ca2+ and ATP. The N-terminal end of yh5LO contained five extra amino acids not present in 5LO purified from human leukocytes. A human 5LO-secretion vector containing the STA1 signal sequence was also constructed. When this hybrid gene was expressed in S. cerevisiae, its product was glycosylated and accumulated in the fractions related to the secretory pathway.

Expression of human 5-lipoxygenase cDNA in Escherichia coli

A cDNA for human 5-lipoxygenase (5LO) was inserted into the vector pKC (constructed from pKK223-3 by replacing its replication origin with that of pUC18) and expressed in Escherichia coli. The enzyme expressed was purified to homogeneity from the cellular soluble fraction. The purified enzyme showed both 5LO and leukotriene A4 synthase activities, which were stimulated by Ca2+ and ATP. Its molecular mass (78 kDa) and NH2-terminal sequence were identical with those of 5LO purified from human leukocytes. The availability of the expression system will facilitate further studies on its regulation and the reaction mechanism of the enzyme.

Amino acid sequence of Mirabilis antiviral protein, total synthesis of its gene and expression in Escherichia coli

We have determined the complete amino acid sequence of Mirabilis antiviral protein (MAP). MAP is composed of 250 amino acids having a combined molecular weight of 27,833 and contains 23 lysine residues and 7 arginine residues. The amino acid sequence of MAP has 24% homology with the Ricin D-A chain. To carry out systematic structure-function studies of MAP, we have accomplished the total synthesis of its gene. We designed a synthetic MAP gene containing 12 unique restriction sites that were on the average 65 base pairs apart. Thirty synthetic oligonucleotides were enzymatically joined to form DNA duplexes. These were strategically synthesized to have EcoRI and HindIII cohesive ends and were cloned in pUC19. Nine blocks of the synthetic fragments were assembled in pUC19 to form the MAP gene consisting of 759 base pairs. The correctness of the connecting reactions was confirmed by step-wise sequencing of each assembled fragment as well as the total gene. When expressed under control of the tac promoter in Escherichia coli, the synthetic gene gave a protein similar to the native MAP. This was confirmed by an enzyme-linked immunosorbent assay and Western blotting analysis.

Duration of ischemia is vital for collateral development: repeated brief coronary artery occlusions in conscious dogs

The effects of two types of repeated transient coronary artery occlusions on collateral development were examined in chronically instrumented, conscious dogs. A 2-minute coronary occlusion at 32-minute intervals (group 1, n = 11) or a 15-second occlusion at 4-minute intervals (group 2, n = 7) were repeated day and night without interruption. In both groups, the total duration of coronary occlusions each day was the same (90 minutes). Before and after repetitive occlusions of either group, effects of transient 2-minute coronary occlusion on regional segment shortening in the ischemic area were examined to assess the functional state of the collateral vessels. In group 1, systolic segment shortening in the area rendered ischemic was reduced to -97.8 +/- 17.7% of the preocclusive control value during 2 minutes of coronary occlusion. After 125-478 repetitive occlusions (3-11 days), the degree of hypokinesia during the 2-minute occlusion was significantly improved to -0.6 +/- 4.6% of the preocclusive value (p less than 0.001 vs. before the repetition). In group 2, it remained unchanged even after 3,500-5,450 repetitive occlusions (11-16 days): -111.8 +/- 8.2% before and -111.4 +/- 13.8% after the repetition of 15-second occlusions (NS). The ratio of peripheral coronary arterial pressure to aortic pressure during transient-coronary occlusion, measured by selective catheterization, was significantly higher in group 1 than in group 2 (64.4 +/- 5.3% vs. 20.7 +/- 1.3%, p less than 0.001). These findings suggest that myocardial ischemia of 2 minutes but not 15 seconds is vital to provide effective stimuli for angiogenesis.

Chronic infusion of norepinephrine into the ventromedial hypothalamus induces obesity in rats

To examine whether chronic increase in the local concentration of certain neurotransmitters in the hypothalamus might lead to some metabolic disorders in peripheral organs, several neurotransmitters and neuropeptides were infused continuously at a rate of 0.48 microliter/h for up to 20 weeks into the unilateral ventromedial (VMH), lateral or paraventricular hypothalamic nucleus of rats. A massive obesity with marked increase in body weight was observed after about 10 weeks when norepinephrine (NE) was infused chronically into the VMH, but not into other hypothalamic loci. Plasma insulin level went up markedly at the early stage of NE infusion and remained high during the infusion period, but plasma glucose did not change appreciably. Similar, but less pronounced effects were observed with epinephrine infusion into the VMH. However, other neurotransmitters and neuropeptides tested had no such effects. The NE-induced obese rats showed hyperphagia and an arrhythmic feeding pattern with increased daytime feeding. Chemical composition and the rate of fatty acid synthesis in the interscapular brown adipose tissue (BAT) were also altered after NE infusion into the VMH: although the triglyceride content was increased, the rate of fatty acid synthesis was decreased, indicating that triglyceride turnover in BAT was greatly reduced. The latter observation suggests that energy dissipation in BAT is impaired and this functional abnormality in BAT may also contribute to the development or maintenance of a new type of hypothalamic obesity induced by NE infusion.

Promotion of flowering in apple trees with gibberellin A4 and C-3 epi-gibberellin A 4

The proportion of spurs flowering on apple trees (Malus domestica Borkh. cv Golden Delicious) displaying a high degree of alternate-year flowering was increased in the "off" year by gibberellin A4 (GA4) and C-3 epi-GA4 applied in the previous year. When applied 4.5 weeks after anthesis amounts of GA4 ranging from 3 to 300 μg per spur and 25 or 50 μg of C-3 epi-GA4 per spur were effective. Treatments with GA4 made seven weeks after anthesis were less effective. A combination of 30 μg GA4 and 30 μg zeatin (6-(4-hydroxy-3-methylbut-trans-2-enylamino)purine) promoted flowering at both treatment times, and tended to be more effective than GA4 alone.

Endogenous indole-3-acetic Acid in the stem of tobacco in relation to flower neoformation as measured by mass spectroscopic assay

The contents of free indole-3-acetic acid (IAA) and alkali-labile, conjugated IAA were measured in relation to a ;floral gradient' present in epidermis and subepidermis tissues of flowering plants of Nicotiana tabacum by capillary gas-chromatographic spectrometric analysis by selected ion monitoring (GC-SIM-MS) using 2,4,5,6,7-penta deutero IA ((2)H(5)-IAA) as an internal standard. In floral axes, floral branches and stems with floral branches, free IAA levels (dry weight) were 387, 253, and 417 nanograms, and bound IAA levels were 99, 1089, and 268 nanograms. In vegetative tissue of the first plus second internodes (measured from top), and of the 11th to 13th internodes, free IAA levels were 826 and 500 nanograms, and bound IAA levels were 1421 and 286 nanograms, respectively. Since flower-forming ability of excised cells from the epidermis and subepidermis shows a gradient in an in vitro system, but levels of IAA in these tissues do not, there thus appears to be no correlation between flower-forming ability (in vitro) and endogenous IAA levels (at the time of excision) in tobacco stem tissues.

[Fundamental and clinical studies on T-1982 (cefbuperazone) in the field of obstetrics and gynecology]

T-1982 (cefbuperazone), a new cephamycin antibiotic, was fundamentally and clinically studied in the field of obstetrics and gynecology. The following results were obtained. The concentrations of T-1982 in arterial and venous blood and genitalia following intravenous injection were measured. The results demonstrated favourable transfer of the drug into various internal genital organs. T-1982 was administered to 12 patients. The efficacy rate was 75.0%, that is to say, good in 9 cases. No side effects were noted in any cases. It is, therefore, presumed that T-1982 is a useful drug for the infectious diseases in the field of obstetrics and gynecology although the number of subjects was not so large in this study.

Quantitation of gibberellins and the metabolism of [(3)H]gibberellin A 1 during somatic embryogenesis in carrot and anise cell cultures

In a carrot (Daucus carota L.) cell line lacking the ability to undergo somatic embryogenasis, and in carrot and anise (Pimpinella anisum L.) cell lines in which embryogenesis could be regulated by presence or absence of 2,4-dichlorophen-oxyacetic acid (2,4-D), in the medium (+2,4-D=no embryogenesis,-2,4-D=embryo differentiation and development), the levels of endogenous gibberellin(s) (GA) were determined by the dwarfrice bioassay, and the metabolism of [(3)H]GA1 was followed. Embryos harvested after 14 d of subculture in-2,4-D had low levels (0.2-0.3 μg g(-1) dry weight) of polar GA (e.g. GA1-like), but much (3-22 times) higher levels of less-polar GA (GA4/7-like); GA1, GA4 and GA7 are native to these cultures. Conversely, the undifferentiated cells in a non-embryogenic strain, and proembryos of an embryogenic strain (+2,4-D) showed very high levels of polar GA (2.9-4.4 μg g(-1)), and somewhat reduced levels of less-polar GA. Cultures of anise undergoing somatic embryo development (-2,4-D) metabolized [(3)H]GA1 very quickly, whereas proembryo cultures of anise (+2,4-D) metabolized [(3)H]GA1 slowly. The major metabolites of [(3)H]GA1 in anise were tentatively identified as GA8-glucoside (24%), GA8 (15%), GA1-glucoside (8%) and the Δ(1(10))GA1-counterpart (2%). Thus, high levels of a GA1-like substance and a reduced ability to metabolize GA1 are correlated with the absence of embryo development, while lowered levels of GA1-like substance and a rapid metabolism of GA1 into GA8 and GA-conjugates are correlated with continued embryo development. Exogenous application of GA3 is known to reduce somatic embryogenesis in carrot cultures; GA4 was found to have the same effect in anise cultures. Thus, a role (albeit negative) in somatic embryogenesis for a polar, biologically active GA is implied.

The endogenous gibberellins of vegetative and reproductive tissue of G2 peas

The gibberellins (GAs) of both vegetative (leaves and stems) and reproductive (pods and seeds) tissue of the G2 strain of peas Pisum sativum L. were characterized in purified extracts by a combination of sequential silicic-acid partition column chromatography, and gas chromatography-mass spectrometry. Gibberellins A19, A20, A29 and an A29 catabolite were identified in both types of tissue. Gibberellins A9, A17 and A44 were also found in pods and seeds.

Changes in Endogenous Gibberellins and the Metabolism of [H]GA(4) after Geostimulation in Shoots of the Oat Plant (Avena sativa)

The recovery from "lodging," or bending over, by shoots of 42-day-old Avena sativa plants is controlled primarily by a negatively geotropic differential growth of the lower halves of the p-1 node-pulvinus and the base of the p-1 internode, relative to the upper halves. Although geostimulation causes a significant reduction in p-1 internode length, dry matter accumulation in the p-1 node-pulvinus is increased, apparently at the expense of the sheath. Recovery to an angle of 30 degrees is associated with changes in endogenous gibberellin-like substances (GAs), and in differential metabolism of applied [(3)H]GA(4) (1.4 Curie per millimole). Although geostimulation depressed total GAs (relative to upright plant parts) to 0.40 and 0.13 for node-pulvini and sheaths, respectively, it increased them 2-fold for internodes. Within the plant part geostimulation increased GAs (relative to upper halves) 29- and 7-fold in lower halves of node-pulvini and internodes, respectively, but reduced GAs to 0.3 in lower halves of sheaths. At age 42 days a GA(4/7)-like (nonpolar) substance predominates, with lesser amounts of a GA(3)-like (polar) substance. Native GAs of Avena include GA(3), GA(4), and GA(7). Geostimulation enhanced the ratio of nonpolar to polar GAs for both halves of internodes, but tended to depress it for sheaths and nodepulvini.The disposition and metabolism of applied [(3)H]GA(4) confirmed the above trends for endogenous GAs regarding localization (e.g. up to 2-fold increases in [(3)H]GA(4) and acidic (3)H-metabolites in the lower halves, relative to upper halves). Also, metabolism into highly water-soluble (3)H-metabolites (biologically inactive conjugates?) was greater (up to 1.8-fold) in upper than in lower halves. The end result of such metabolic trends would be to reduce acidic (biologically active?) GAs in the upper half, while retaining them for a longer time in the lower half.Geotropically stimulated Avena shoots thus increase, within 24 hours, the levels of acidic GAs in the lower halves of the p-1 node-pulvinus and p-1 internode, the two plant parts responsible for the geostimulated growth.