Enzyme-entrapping behaviors in alginate fibers and their papers

Enzyme immobilization in the form of fiber and paper was easily achieved by wet spinning of aqueous admixture of sodium alginate and enzymes into divalent metallic ion solution as a coagulating bath, followed by paper making of resultant shortly cut fibers. Entrapment yields of enzymes used, e.g., glucoamylase, cyclodextrin glucanotransferase, endo-polygalacturonase, and protease, were always higher in calcium alginate fibers and their papers than those in corresponding beads. It was found that the yields increased with an increase of the discharge rate through the spinning nozzle because the higher discharge rate could provide more highly oriented metal-chelate linear polymer molecules along the fiber axis for preventing leakage of entrapped enzymes. Divalent metallic ions affected greatly the entrapment of glucoamylase in alginate fibers, the order of which followed roughly the ionotropic series of Thiele. Entrapment of glucoamylase in bicomponent systems comprising alginate and other water-soluble polymers was also investigated.     

Calcium-sensitive cls4 mutant of Saccharomyces cerevisiae with a defect in bud formation.

A calcium-sensitive cls4 mutant of Saccharomyces cerevisiae ceased dividing in the presence of 100 mM CaCl2, producing large, round, unbudded cells. Since its DNA replication and nuclear division still continued after interruption of normal budding, the cls4 mutant had a defect in bud formation in Ca2+-rich medium. Its calcium content and calcium uptake activity were the same as those of the wild-type strain, suggesting that the primary defect of the mutation was not in a Ca2+ transport system. Genetic analysis showed that the cls4 mutation did not complement the cdc24-1 mutation, which is known to be a temperature-sensitive mutation affecting bud formation and localized cell surface growth at a restrictive temperature. Moreover, cls4 was tightly linked to cdc24, and a yeast 3.4-kilobase-pair DNA fragment carrying both the CLS4 and CDC24 genes was obtained. These results suggest that the cls4 mutation is allelic to the cdc24 mutation. Thus, Ca2+ ion seems to control bud formation and bud-localized cell surface growth.     

The CLS2 gene encodes a protein with multiple membrane-spanning domains that is important Ca2+ tolerance in yeast

Genetic screening of Saccharomyces cerevisiae mutants defective in Ca²⁺ homeostasis identified cls2, which exhibits a specific Ca²⁺-sensitive growth phenotype. We describe here the CLS2 gene and a multicopy suppressor (named BCL21, for bypass of CLS2) of the cls2 mutation. The CLS2 gene encodes a polypeptide of 410 amino acid residues, and its hydropathy profile indicates that the predicted Cls2 protein (Cls2p) contains ten putative membrane spanning regions. Immunofluorescent staining of the yeast cells expressing epitopetagged Cls2p suggests that Cls2p is localized to endoplasmatic reticulum (ER) membrane. A cls2 disruption strain is viable, but shows a Ca²⁺-sensitive phenotype like the original cls2 mutants. BCL21 suppresses the cls2 disruption mutation, indicating that the multicopy suppression does not require the Cls2p. Suppression of cls2 was observed even after introduction of a singlecopy plasmid harboring BCL21. The BCL21 gene encodes a protein of 382 amino acid residues and is identical to the SUR1 gene. sur1 was originally isolated as a suppressor of rvs161, which has reduced viability in nutrient starvation conditions. Possible mechanisms of the multicopy suppression are discussed.     

Suppression of yeast geranylgeranyl transferase I defect by alternative prenylation of two target GTPases, Rho1p and Cdc42p.

Geranylgeranyl transferase I (GGTase I), which modifies proteins containing the sequence Cys-Ali-Ali-Leu (Ali: aliphatic) at their C-termini, is indispensable for growth in the budding yeast Saccharomyces cerevisiae. We report here that GGTase I is no longer essential when Rho1p and Cdc42p are simultaneously overproduced. The lethality of a GGTase I deletion is most efficiently suppressed by provision of both Rho1p and Cdc42p with altered C-terminal sequences (Cys-Ali-Ali-Met) corresponding to the C-termini of substrates of farnesyl transferase (FTase). Under these circumstances, the FTase, normally not essential for growth of yeast, becomes essential.     

Purification and characterization of pig lung carbonyl reductase.

A pyrazole-sensitive carbonyl reductase from pig lung was purified to homogeneity by electrophoretic criteria. Chemical cross-linking study suggested that the native enzyme is a tetramer with a Mr of 103,000, consisting of apparent identical subunits of Mr 24,000. The enzyme reduced aliphatic and aromatic carbonyl compounds with NADPH as a preferable cofactor to NADH and catalyzed the oxidation of secondary alcohols and the aldehyde dismutation in the presence of NAD(P)+. Immunohistochemical study with the antibodies against the enzyme revealed that the enzyme was localized in the ciliated cells, nonciliated bronchiolar cells, Type II alveolar pneumocytes, and the epithelial cells of the ducts of the bronchial glands in the pig lung. In addition to the properties and distribution, the pig lung enzyme was immunochemically similar to the pulmonary enzymes in the guinea pig and mouse. However, the pig enzyme showed the following unusual features. (1) The enzyme exhibited an equatorial specificity in the reduction of 3-ketosteroids; the 4-pro-S hydrogen of NADPH was transferred to the carbonyl carbon atom of 5 alpha- and 5 beta-androstanes, and the respective reduced products were identified as 3 beta- and 3 alpha-hydroxysteroids. (2) Although the NADPH-linked reduction of carbonyl compounds apparently obeyed the Michaelis-Menten kinetics at pH 6.0, the double-reciprocal plots of the velocity vs concentrations of the carbonyl substrates were convex at pH higher than 6.5. The Hill coefficients and [S]0.5 values for the substrates decreased as the pH for reaction increased. The results suggest that the pig enzyme exhibits negative cooperativity with respect to the carbonyl substrates and that the hydrogen ion acts as an allosteric effector abolishing the negative interaction.     

Down modulation of N-myc, heat-shock protein 70, and nucleolin during the differentiation of human neuroblastoma cells.

Cultured human neuroblastoma (GOTO) cells were induced to differentiate by dibutyryl cyclic AMP (Bt2cAMP) and/or retinoic acid (RA). A combination of Bt2cAMP (1 mM) and RA (1 microM) yielded the most significant networks of neurites after 3 to 4 days, this being associated with the reduction of N-myc mRNA levels. Next, we examined several cellular genes that were possibly linked with changes in N-myc gene expression under these conditions. Among the genes examined, both nucleolin and a major heat-shock protein (hsp70) mRNAs showed changes concomitant with those in N-myc mRNA levels when induced by Bt2cAMP and RA. Dibutyryl cAMP alone induced several short cellular processes and caused a marked decrease in N-myc mRNA within 2 days. RA alone induced a few long and straight neurites along the longitudinal axis of individual cells and a significant decrease in growth rate but showed neither network formation nor a decrease in N-myc gene expression. These results indicate differential effects of Bt2cAMP and RA on the regulatory mechanisms of both cell proliferation and differentiation and also indicate a possible association of expression of N-myc gene with those of hsp70 and nucleolin genes.     

Fast Na+ channels in smooth muscle from pregnant rat uterus.

Smooth muscle cells normally do not possess fast Na+ channels, but inward current is carried through two types of Ca2+ channels: slow (L type) Ca2+ channels and fast (T type) Ca2+ channels. Whole-cell voltage clamp was done on single smooth muscle cells isolated from the longitudinal layer of the 18-day pregnant rat uterus. Depolarizing pulses, applied from a holding potential of -90 mV, evoked two types of inward current, fast and slow. The fast inward current decayed within 30 ms, depended on [Na]o, and was inhibited by tetrodotoxin (TTX) (K0.5 = 27 nM). The slow inward current decayed slowly, was dependent on [Ca]o (or Ba2+), and was inhibited by nifedipine. These results suggest that the fast inward current is a fast Na+ channel current and that the slow inward current is a Ca2+ slow channel current. A fast-inactivating Ca2+ channel current was not evident. We conclude that the ion channels that generate inward currents in pregnant rat uterine cells are TTX-sensitive fast Na+ channels and dihydropyridine-sensitive slow Ca2+ channels. The number of fast Na+ channels increased during gestation. The averaged current density increased from 0 on day 5, to 0.19 on day 9, to 0.56 on day 14, to 0.90 on day 18, and to 0.86 pA/pF on day 21. This almost linear increase occurs because of an increase in the fraction of cells that possess fast Na+ channels. The Ca2+ channel current density was also higher during the latter half of gestation. These results indicate that the fast Na+ channels and Ca2+ slow channels in myometrium become more numerous as term approaches, and we suggest that the fast Na+ current may be involved in spread of excitation. Isoproterenol (beta-agonist) did not affect either ICa(s) or INa(f), whereas Mg2+ (K0.5 = 12 mM) and nifedipine (K0.5 = 3.3 nM) depressed ICa(s). Oxytocin had no effect on INa(f) and actually depressed ICa(s) to a small extent. Therefore, the tocolytic action of beta-agonists cannot be explained by an inhibition of ICa(s), whereas that of Mg2+ can be so explained. The stimulating action of oxytocin on uterine contractions cannot be explained by a stimulation of ICa(s).     

Yeast calmodulin localizes to sites of cell growth

Summary Intracellular localization of calmodulin was examined in the budding yeast,Saccharomyces cerevisiae. Distribution of calmodulin changes in a characteristic way during the cell cycle. Calmodulin localizes to a patch at the presumptive bud site of unbudded cells. It concentrates at the bud tip in small-budded cells, and later it diffuses throughout the entire bud. At cytokinesis, calmodulin is largely at the neck between the mother and daughter cells. Double staining experiments have shown that the location of some polarized actin dots is coincident with that of calmodulin dots. Polarized localization of actin dots is observed in cells depleted of calmodulin, suggesting that calmodulin is not required for localization of the actin dots. Thecdc24 mutant that has a defect in bud assembly at the restrictive temperature fails to exhibit polarized localization of calmodulin, indicating that theCDC24 gene product is responsible for controlling the polarity of calmodulin.     

A DBL-homologous region of the yeast CLS4/CDC24 gene product is important for Ca(2+)-modulated bud assembly.

The CLS4/CDC24 is essential for the budding process of the yeast Saccharomyces cerevisiae. Disruption of the CLS4/CDC24 gene is lethal, and expression of the CLS4 product under the control of the GAL1 promoter is sufficient for cellular growth. The CLS4 product is detected in yeast cell lysate with an apparent molecular mass of 93 kD (854 amino acid residues) and shows homology with the human DBL oncogene product. Temperature-sensitive cdc24-1 mutation is located in the N-terminal portion of the protein whereas Ca(2+)-sensitive cls4-1 mutation is present after the DBL-homologous region (amino acid residues 281-518) near the putative Ca(2+)-binding site. Mutations within the DBL-homologous region are responsible for the Ca(2+)-sensitive phenotype. Thus the CLS4 gene product seems to have several functional domains within the molecule essential for bud assembly.