Glycerol and dihydroxyacetone dissimilation in Desulfovibrio strains

During growth on glycerol two marine Desulfovibrio strains that can grow on an unusually broad range of substrates contained high activities of glycerol kinase, NAD(P)-independent glycerol 3-phosphate dehydrogenase and the other enzymes necessary for the conversion of dihydroxyacetone phosphate to pyruvate. Glycerol dehydrogenase and a specific dihydroxyacetone kinase were absent. During growth on dihydroxyacetone, glycerol kinase is involved in the initial conversion of this compound to dihydroxyacetone phosphate which is then further metabolized. Some kinetic properties of the partially purified glycerol kinase were determined. The role of NAD as electron carrier in the energy metabolism during growth of these strains on glycerol and dihydroxyacetone is discussed.Glycerol also supported growth of three out of four classical Desulfovibrio strains tested. D. vulgaris strain Hildenborough grew slowly on glycerol and contained glycerol kinase, glycerol 3-phosphate dehydrogenase and enzymes for the dissimilation of dihydroxyacetone phosphate. In D. gigas which did not grow on glycerol the enzymes glycerol kinase and glycerol 3-phosphate dehydrogenase were absent in lactate-grown cells.Abbreviations DHA dihydroxyacetone - DHAP dihydroxyacetone phosphate - G3P glycerol 3-phosphate - GAP glyceraldehyde 3-phosphate - 3-PGA 3-phosphoglycerate - 2-PGA 2-phosphoglycerate - 2,3-DPGA 2,3-diphosphoglycerate - PEP phosphoenolpyruvate - DH dehydrogenase - GK glycerol kinase - DHAK dihydroxyacetone kinase - TIM triosephosphate isomerase - PGK 3-phosphoglycerate kinase - PK pyruvate kinase - LDH lactate dehydrogenase - DTT dithiotreitol - HEPES 4-(2-hydroxyethyl)-1-piperazine ethane sulfonic acid - PIPES piperazine-1,1-bis(2-ethane sulfonic acid) - BV²⁺/BV⁺ oxidized/reduced benzylviologen - PMS phenazine methosulfate - DCPIP 2,6-dichlorophenolindophenol - MTT 3-(4,5-dimethylthiazol-2-yl)-2,4-diphenyltetrazolium bromide     

Effects of NaCl on Metabolic Heat Evolution Rates by Barley Roots

The effect of salinity stress on metabolic heat output of barley (Hordeum vulgare L.) root tips was measured by isothermal microcalorimetry. Several varieties differing in tolerance to salinity were compared and differences quantified. Two levels of inhibition by increasing salt were found. Following the transition from the initial rate to the first level, inhibition remained at about 50% with further increases in salt concentration up to 150 millimolar. The concentration of salt required to inhibit to this level was cultivar dependent. At higher concentrations (>150 millimolar) of salt, metabolism was further decreased. This decrease was not cultivar dependent. The decreased rate of metabolic heat output at the first transition could be correlated with decreases in uptake of NO₃⁻, NH₄⁺, and Pi that occurred as the salt concentration was increased. The high degree of dependence of the inhibition of metabolic heat output on NaCl concentration points to a highly cooperative reaction responsible for the general inhibition of metabolism and nutrient uptake. The time required to attain the first level of salt inhibition is less than 20 minutes. Inhibition of root tips was not reversible by washing with salt free solutions. In addition to revealing these features of salt inhibition, isothermal microcalorimetry is a promising method for convenient and rapid determination of varietal differences in response to increasing salinity.     

Biosynthesis of intestinal microvillar proteins. Low temperature arrests both processing and intracellular transport

The effect of culture at 20 degrees C on biosynthesis of microvillar enzymes was studied in pig small intestinal mucosal explants. At this temperature, aminopeptidase N (EC 3.4.11.2) and sucrase-isomaltase (EC 3.2.1.48-10) both accumulated intracellularly, predominantly in their transient, high mannose-glycosylated form characteristic of the newly synthesized enzymes prior to the molecular processing taking place in the Golgi complex. The general morphology of the enterocyte was unaffected by culture at low temperature except for the Golgi complex where the cisternae appeared condensed and surrounded by numerous vesicles of 50 to 55 nm. Both molecular processing and microvillar expression could be restored by shifting the temperature to 37 degrees C. Culture at low temperature did not induce any missorting of newly synthesized aminopeptidase N, but both molecular processing and microvillar expression only resumed at a slow rate after increasing the temperature, suggesting that reorganization of the Golgi complex is a time-requiring process.     

The glue protein of ribbed mussels (Geukensia demissa): a natural adhesive with some features of collagen

Summary The Atlantic ribbed musselGeukensia (Modiolus)demissa attaches itself to the roots of cord grass and other hard objects in tidal salt marshes by spinning adhesive byssal threads. The precursor of a protein apparently present in the adhesive plaques of the threads was isolated in quantity from the foot of the mussel. The protein has an apparent molecular weight of 130000, a pI of 8.1, and contains a high proportion of Gly, Glu/Gln, Lys and 3,4-dihydroxyphenyl-l-alanine (DOPA). Sequence of tryptic peptides suggests a pattern of repeated motifs, such as: Gly-DOPA-Lys, and X-Gly-DOPA-Y-Z-Gly-DOPA/Tyr-Lys, where X is Thr or Ala in octapeptides and Gln-Thr in nonapeptides. Y is variable, but more often than not hydrophobic; and Z is frequently Pro or 4-trans-hydroxyproline (Hyp). The presence of Pro-Gly and Hyp-Gly sequences of -hydroxylysine in the protein is reminiscent of typical collagens; however, the protein is not labile to clostridial collagenase, nor does collagen cross-react with antibodies raised against the mussel protein. Unlike typical collagens, Gly probably occurs only at every 4th or 5th residue in this unusual mussel protein.Abbreviations Anti-Gdfp anti-G. demissa foot protein - Dopa 3,4-dihydroxyphenylalanine - CTAB cetyltrimethylammonium bromide - HPLC high performance liquid chromatography - PAGE polyacrylamide gel electrophoresis Supported by grants from the National Science Foundation (DMB 8500301) and the Office of Naval Research (N00014-86K-0717)     

Quantitative determination of Ca2+-dependent Mg2+-ATPase from sarcoplasmic reticulum in muscle biopsies.

The possibility of quantifying the total concentration of Ca2+-dependent Mg2+-ATPase of sarcoplasmic reticulum was investigated by measurement of the Ca2+-dependent steady-state phosphorylation from [gamma-32P]ATP and the Ca2+-dependent 3-O-methylfluorescein phosphatase (3-O-MFPase) activity in crude muscle homogenates. The Ca2+-dependent phosphorylation at 0 degree C (mean +/- S.E.) was 40.0 +/- 2.5 (n = 6) and 6.2 +/- 0.7 (n = 4) nmol/g wet wt. in rat extensor digitorum longus (EDL) and soleus muscle, respectively (P less than 0.001). The Ca2+-dependent 3-O-MFPase activity at 37 degrees C was 1424 +/- 238 (n = 6) and 335 +/- 56 (n = 4) nmol/min per g wet wt. in rat EDL and soleus muscle, respectively (P less than 0.01). The molecular activity calculated from these measurements amounted to 35 +/- 5 min-1 (n = 6) and 55 +/- 10 min-1 (n = 4) for EDL and soleus muscle respectively. These values were not different from the molecular activity calculated for purified Ca2+-ATPase (36 min-1). The Ca2+-dependent 32P incorporation in soleus muscle decreased in the order mice greater than rats greater than guinea pigs. In EDL muscles from hypothyroid rats at a 30% reduction of the Ca2+-dependent phosphorylation was observed. The Ca2+-dependent phosphorylation in vastus lateralis muscle from three human subjects amounted to 4.5 +/- 0.8 nmol/g wet wt. It is concluded that measurement of the Ca2+-dependent phosphorylation allows rapid and reproducible quantification of the concentration of Ca2+-dependent Mg2+-ATPase of sarcoplasmic reticulum. Since only 20-60 mg of tissue is required for the measurements, the method can also be used for biopsies obtained in clinical studies.     

Presence of the major progesterone-induced proteins of the sheep endometrium in fetal fluids

Allantoic and amniotic fluids were collected on Days 60 (n = 3), 100 (n = 4), and 140 (n = 3) of pregnancy. The presence of uterine milk proteins (UTM-proteins) in these samples was evaluated by Ouchterlony immunodiffusion and enzyme-linked immunoabsorbant assay (ELISA). Eight of ten samples of allantoic fluid and three of ten samples of amniotic fluid produced one or two immunoprecipitin bands against antiserum to UTM-proteins. Each band fused with immunoprecipitin bands from UTM-proteins purified from uterine fluid. Data from a semi-quantitative ELISA indicated that allantoic fluid from all ewes and amniotic fluid from six of ten ewes contained immunoreactive UTM-proteins. Concentrations of UTM-proteins in these fluids were not statistically affected by day of gestation (p greater than 0.10), but tended to decline as gestation advanced. Greater concentrations of UTM-proteins were detected in allantoic fluid than in amniotic fluid (p less than 0.05). The physical characteristics of the immunoreactive material in allantoic and amniotic fluids were examined by polyacrylamide gel electrophoresis and Western blotting. The immunoreactive material was found to possess pIs and molecular weights identical to UTM-proteins. These results indicate that fetal fluids contain material that reacts with antiserum to UTM-proteins and has physical properties similar to UTM-proteins. It is likely, therefore, that the UTM-proteins are transported across the placenta during gestation, perhaps to serve some function in the fetal compartment.     

Kinetics and in vitro origin of the temperature-dependent transition of the estrogen receptor monomer

Partitioning of estrogen receptors in aqueous two-phase polymer systems has provided the basis for a detailed kinetic analysis of the effects of temperature on estrogen receptor (ER) structure in vitro. Exposure to temperatures of 0-30 degrees C increased the rate of change in ER partition coefficients by up to 100-fold but did not affect the final extent of the process. The temperature-dependent change in ER partition coefficients was characterized by a linear Arrhenius plot and an activation energy of 25 kcal/mol. The rate of the temperature-dependent ER transition (28 degrees C) was found to be unaffected by greater than 50-fold changes in receptor concentration, which indicates that the temperature-dependent change in partition coefficients reflects a first-order process. The partition coefficients of heated ER were unaffected by subsequent 18-h incubations at 0 degree C, indicating that the temperature-dependent ER transition is irreversible in vitro. Direct heating of the unoccupied ER resulted in both a change in ER partition coefficients and a loss of ER binding sites. The temperature-dependent change in unoccupied ER partition coefficients was complete within 30 min at 28 degrees C and yielded a first-order rate constant that was the same as that obtained for heating the receptor-estradiol complex at 28 degrees C. In contrast, the loss of unoccupied ER binding sites that occurred during 28 degrees C incubations did not reach completion after 150 min of heating and was found to behave as a second-order process.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cathepsin B secretion by rabbit articular chondrocytes: modulation by cycloheximide and glycosaminoglycans

Rabbit articular chondrocytes in monolayer culture are modulated away from their differentiated state and undergo morphological and biochemical changes. One of the characteristics of the modulated state is an abnormally high production of the cysteine endopeptidase cathepsin B. Addition to chondrocyte cultures of the protein biosynthesis inhibitor, cycloheximide, resulted in a concentration-dependent reduction of cathepsin B secretion, which was fully restored after removal of cycloheximide. Glycosaminoglycans added to the culture medium of modulated chondrocytes partially reduced the rate of secretion of cathepsin B, this effect being dependent on their structure, the degree of sulfation, and concentration. The age of the chondrocytes and the duration of the treatment also influenced this response. The switching off of cathepsin B release was apparently best favored by a high concentration of negatively charged sulfate groups attached to a polymeric glycosaminoglycan chain; this simulates the natural environment of the chondrocytes in articular cartilage.