Protein rotation, enzyme activity and photooxidation of SH groups in sarcoplasmic reticulum Ca2+-ATPase

The binding of probe molecules such as fluorescein isothiocyanate, eosin isothiocyanate and erythrosin isothiocyanate to the Ca2+-ATPase of sarcoplasmic reticulum followed by illumination of the labelled protein causes substantial reductions of ATPase activity over a 1-h period. The degree of light-sensitivity induced by these probes is related to the triplet yield of these probe molecules. Consistent with this, the greatest effect is seen with erythrosin isothiocyanate and the least effect with fluorescein isothiocyanate. These reductions of ATPase activity associated with illumination are also associated with an aggregation of the protein molecules. This is indicated by laser flash photolysis measurements and also by polyacrylamide gel electrophoresis. A reduction in the number of thiol groups present on the ATPase molecule parallels the reduction of enzyme activity and changes in the protein mobility. The results are discussed in relation to the use of these probe molecules to study biological systems and also in terms of oxidative processes which may affect protein function in vivo.     

Multiple wavelength illumination in flow cytometry using a single arc lamp and a dispersing element

The principle of a multiple wavelength illumination method for flow cytometers, based upon a combination of a helium-neon laser and an arc lamp as illumination sources is described. By using a prism, the light from the arc lamp is dispersed and the different colors are imaged at different places on the sample stream. The small angle light scattering from the helium-neon laser light is measured as a relevant parameter and serves as a trigger signal for subsequent measurements of fluorescence or scattering of light from the arc lamp. Two experimental systems are described utilizing this principle: a system where the emission is detected orthogonally with respect to the direction of the illumination beams, and an epi-illumination system. With the orthogonal set-up multiple wave-length right angle scattering measurements are possible. This is illustrated by showing that the orthogonal scattering from erythrocytes is strongly dependent on the illumination wavelength. It is further shown that the apparatus is suitable for the measurement of intracellular pH using the pH dependence of the excitation spectrum of fluorescein. The epi-illumination system allows excitation of two (or more) fluorescent dyes with different excitation spectra. In this case the emission spectra of the fluorescent dyes may overlap substantially. This is shown by simultaneous measurement of DNA and protein of Chinese hamster lung cells using mitramycin and tetramethyl rhodamin isothiocyanate (TRITC).     

A Glycoprotein from Rat Liver Endoplasmic Reticulum Promotes Both Aggregation and Fusion of Liposomes at Acidic pH

Low-pH-induced fusion of liposomes with rat liver endoplasmic reticulum was evidenced. Fusion was inactivated by treatment of microsomes with trypsin or EEDQ (N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline), indicating the involvement of a protein. The protein was purified 555-fold by chromatographic steps. The identification and purification to homogeneity was obtained by electroelution from a slab gel, which gave a still active protein of about 50 kDa. The protein promoted the fusion of liposomes; laser light scattering showed an increase of mean radius of vesicles from 60 up to about 340 nm. Fusion was studied as mass action kinetics, describing the overall fusion as a two-step sequence of a second order aggregation followed by a first order fusion of liposomes. For phosphatidylcholine containing liposomes aggregation was not rate-limiting at pH 5.0 and fusion followed first order kinetics with a rate constant of 13 · 10⁻³ sec⁻¹. For phosphatidylethanolamine/phosphatidic acid liposomes aggregation was rate-limiting; however, the overall fusion was first order process, suggesting that fusogenic protein influences both aggregation and fusion of liposomes. The protein binds to the lipid bilayer of liposomes, independently of pH, probably by a hydrophobic segment. Exposed carboxylic groups might be able to trigger pH-dependent aggregation and fusion. It is proposed that the protein inserted in the lipid bilayer bridges with an adjacent liposome forming a fused doublet. Since at endoplasmic reticulum level proton pumps are operating to generate a low-pH environment, the membrane bound fusogenic protein may be responsible for both aggregation and fusion of neighboring membranes and therefore could operate in the exchange of lipidic material between intracellular membranes. Received: 25 August 1997/Revised: 28 April 1998     

Photoinduced cell killing and crosslinking of fluorescein conjugated concanavalin A to cell surface proteins

Bleaching of fluorescein conjugated concanavalin A (F-Con A) labelled plasma membranes with 488 nm laser light leads to some broadening and a loss of protein bands and the appearance of high molecular weight material as shown by sodium dodecylsulfate polyacrylamide gel electrophoresis, indicating membrane protein crosslinking. The F-Con A is found throughout the high molecular weight regions linked to other proteins in large aggregates. Irradiation of whole cells labelled with F-Con A leads to cell death. These effects are dependent upon total light exposure and F-Con A concentration.     

Mutual stimulation of temperature and light effects on C(4) phosphoenolpyruvate carboxylase in leaf discs and leaves of Amaranthus hypochondriacus

This article reports marked modulation of the activity and regulatory properties of phosphoenolpyruvate carboxylase (PEPC) by temperature and light in leaf discs as well as leaves of Amaranthus hypochondriacus. The activity of PEPC increased by 1.7-fold at 45 degrees C over 25 degrees C. Warm temperature also stimulated the photoactivation of PEPC. The activation by light of PEPC was 1.9-fold at 25 degrees C and increased to 2.2-fold at 45 degrees C. The sensitivity of PEPC to its inhibitor malate was less and the activation by glucose-6-phosphate (G-6-P) or inorganic phosphate (Pi) was more at 45 degrees C than that at 25 degrees C. These effects of temperature were quite pronounced in light. Similar responses were observed when detached leaves were exposed to varying ambient temperature (dry heat). The activity of PEPC increased by 1.6-fold at 45 degrees C over 25 degrees C in the dark. The activation of PEPC by light was 2.1-fold at 25 degrees C and increased to 2.6-fold at 45 degrees C. Inhibition by malate was less and activation by G-6-P or Pi was more at 45 degrees C than that at 25 degrees C. Thus, there was a marked modulation of not only the activity but also the regulatory properties of the enzyme by temperature and light, independently as well as cooperatively with each other. Further experiments suggested that PEPC was able to memorize to a significant extent the changes induced by warm temperature and that these changes were complemented by subsequent illumination. These effects were not due to changes in PEPC protein levels. We conclude that temperature and light can modulate PEPC activity and regulatory properties not only individually but also in a significantly cooperative manner with each other. As significant increases in temperature are common during daytime in tropical or subtropical conditions, we suggest that the synergistic effects of temperature and light are quite relevant in optimizing the activity of PEPC in leaves of C(4) plants.     

Purification and characterization of human liver beta-galactosidase from a patient with the adult form of GM1 gangliosidosis and a normal control

beta-Galactosidases were purified to homogeneity from livers of a normal control and a patient with the adult form of GM1 gangliosidosis. The purification was achieved by chromatography on DEAE-Sepharose fast flow, Con A-Sepharose, p-aminophenyl-1-thio-beta-D-galactopyranoside-Sepharose, and QAE-Mono Q. The normal and mutant enzymes were purified about 5000-fold with a yield of 10% and 1800-fold with a yield of 34%, respectively, and could hydrolyze 4-methylumbelliferyl-beta-D-galactoside, GM1 ganglioside, and asialofetuin. The purified normal enzyme was eluted from a TSK gel G-4000SW column as three symmetrical peaks of protein which were coincident with the three peaks of enzyme activity. The enzyme in these three peaks had apparent molecular weights of 800,000 (polymer), 140,000 (dimer), and 65,000 (monomer), whereas the mutant enzyme was eluted as two symmetrical peaks of protein and enzyme activity. The apparent molecular weight of a major monomeric form of the enzyme (beta-galactosidase A) was 60,000, and no dimeric form of the enzyme existed. Normal and mutant purified enzyme preparations migrated as a single major protein band with apparent molecular weights of 65,000 or 60,000, respectively, by SDS-polyacrylamide gel electrophoresis after treatment with mercaptoethanol. On isoelectric focussing, the mutant enzyme migrated more anodally than the normal enzyme. The mutant enzyme also had altered enzyme properties, such as pH optimum, Km values, substrate specificity and heat-stability. These data on the characteristics of the purified enzyme preparations provide the first direct evidence that patients with the adult form of GM1 gangliosidosis have a structurally altered beta-galactosidase.     

Evidences from Action Spectra for a Specific Participation of Chlorophyll b in Photosynthesis

Rate of oxygen evolution in photosynthesis was measured as the current from a polarized platinum electrode covered by a thin layer of Chlorella. The arrangement gave a reproducibly measurable rate of photosynthesis proportional to light intensity at the low levels used and gave rapid response to changes in illumination. Two phenomena have been explored. The Emerson effect was observed as an enhancement of photosynthesis in long wavelength red light (700 mµ) when shorter wavelengths were added. Two light beams of wavelengths 653 and 700 mµ when presented together gave a photosynthetic rate about 25 per cent higher than the sum of the rates obtained separately. Large and reproducible transients in rate of oxygen evolution were observed accompanying change in illumination between two wavelengths adjusted in intensity to support equal steady rates of photosynthesis. The transients were found not to be specifically related to long wavelength red light. Both enhancement and the transients have identical action spectra which are interpreted as demonstrating a specific photochemical participation of chlorophyll b.     

Light-induced Changes in the Pattern of Protein Synthesis during the Early Stages of Greening of Etiolated Maize Leaves

The effect of light on protein synthesis during the early stages of greening of etiolated maize (Zea mays) leaves was studied using double labeling with leucine and fractionation of proteins by gel filtration and acrylamide gel electrophoresis. The incorporation of labeled leucine into a relatively small number of plastid proteins is effected within the first 30 to 60 minutes of illumination. These proteins do not accumulate with time. When illumination is prolonged, additional proteins are effected.     

A sensitive method for the detection of beta-galactosidase in transfected mammalian cells.

A sensitive method has been developed for the detection of E. coli beta-galactosidase in transfected HeLa cells. The chromogenic substrate, CPRG (chlorophenol red-beta-D-galactopyranoside), was compared with ONPG (o-nitrophenyl-beta-D-galactopyranoside) by kinetic analysis with purified beta-galactosidase. The Km for CPRG was 1.35 mM and the Vmax was 21.4, whereas the Km for ONPG was 2.42 and the Vmax was 41.1. CPRG at 8.0 mM (6-fold Km) gave 86% of the Vmax and was used as the standard concentration for quantitation of enzyme levels. The Vmax for CPRG was half that for ONPG, and chlorophenol red has an extinction coefficient that is 21-fold higher than o-nitrophenol; these factors make CPRG about 10-fold greater in sensitivity for the quantitation of enzyme levels. The use of Nonidet P-40 to lyse the cells and the use of CPRG as substrate permitted the rapid detection of low levels of enzyme production from transfected human cells that could not be detected using ONPG.     

Purification and characterization of GM1 ganglioside beta-galactosidase from normal feline liver and brain.

GM1 ganglioside beta-galactosidase (GM1-beta-galactosidase) was purified from normal cat brain and liver by a combination of classical and affinity procedures. The final preparation of brain GM1-beta-galactosidase was enriched over 2000-fold with a 36% yield. However, the product was shown to contain several components by disc gel electrophoresis. GM1-beta-galactosidase was also purified from liver with greater than a 30 000-fold enrichment and 40% yield. The liver enzyme was judged homogeneous by disc gel electrophoresis at pH 4.3, 8.1, and 8.9 and by gel chromatography. Both liver and brain GM1-beta-galactosidase(s) eluted as sharp symmetrical peaks from Sephadex G-200 with molecular weights of 250 000 +/- 50 000. The apparent Km determined for 4-methylumbelliferyl beta-D-galactopyranoside (4-MU-Gal) using partially purified brain GM1-beta-galactosidase was 1.73 X 10(-4) M. Liver GM1-beta-galactosidase gave a Km with 4-MU-Gal of 3.25 X 10(-4) M and for [3H]GM1 ganglioside a Km of 4.51 X 10(-4) M was calculated. The pH optima of brain and liver GM1-beta-galactosidase using 4-MU-Gal was 3.8-4.5. By contrast, liver GM1-beta-galactosidase gave a sharp activity peak at pH 4.2 with [3H]GM1 ganglioside. Inhibition by mercuric chloride and sensitivity to hydrogen peroxide and persulfate suggest the involvement of a sulfhydryl in catalysis.     

Autoregulation of the stability operon of IncFII plasmid NR1.

The stb locus of IncFII plasmid NR1, which mediates stable inheritance of the plasmid, is composed of an essential cis-acting DNA site located upstream from two tandem genes that encode essential stability proteins. The two tandem genes, stbA and stbB, are transcribed as an operon from promoter PAB. Using PAB-lacZ gene fusions, it was found that the stb operon is autoregulated. A low-copy-number stb+ plasmid introduced into the same cell with the PAB-lacZ fusion plasmid repressed beta-galactosidase activity about 5-fold, whereas a high-copy-number stb+ plasmid repressed beta-galactosidase about 15-fold. The details of autoregulation were analyzed by varying the concentrations of StbA and StbB to examine their effects on expression from the PAB-lacZ fusion plasmid. StbB protein by itself had autorepressor activity. Although StbA protein by itself had no detectable repressor activity, plasmids that encoded both stbA and stbB repressed more effectively than did those that encoded stbB alone. Plasmids with a mutation in stbA had reduced repressor activity. One mutation in stbB that inactivated the stability function also reduced, but did not eliminate, repressor activity. Repressor activity of the mutant StbB protein was effectively enhanced by stbA. These results indicate that StbB serves two functions, one for stable inheritance and one for autoregulation of the stb operon, both of which may be influenced by StbA protein.     

Regulated high-level expression of the Herpes simplex type I thymidine kinase gene in Escherichia coli

A plasmid-borne Herpes simplex virus type 1 (HSV-1) thymidine kinase (TK) gene (tk) was expressed in Escherichia coli by inserting a 203-bp lacL8/UV5 promoter-operator segment, in frame, 53 bp 5' to the native tk translational start codon. The hybrid gene created by this fusion encodes a polypeptide which has 25 additional amino acids on the amino terminus of the HSV-1 TK protein and phenotypically complements a tdk- mutation of E. coli. This fusion polypeptide has been characterized by maxicell, immunoprecipitation, and native gel techniques, and its activity is inhibited by anti-HSV-1 antibody. In a tk expressor strain containing a F' lacIq (which overproduces the lactose repressor), the isopropyl-beta-D-thiogalactoside (IPTG) causes greater than 1000-fold coordinate induction of the plasmid-encoded TK and chromosomal beta-galactosidase activities. Pulse-chase induction demonstrates the fused TK polypeptide to be as stable as beta-galactosidase. HSV-1 tk-specific RNA isolated from this bacterial strain has a short half-life characteristic of bacterial messages.     

Purification and properties of GM1 ganglioside beta-galactosidases from bovine brain

Two GM1-beta-galactosidases, beta-galactosidases I, and II, have been highly purified from bovine brain by procedures including acetone and butanol treatments, and chromatographies on Con A-Sepharose, PATG-Sepharose, and Sephadex G-200. beta-Galactosidase I was purified 30,000-fold and beta-galactosidase II 19,000-fold. Both enzymes appeared to be homogeneous, as judged from the results of polyacrylamide disc gel electrophoresis. Enzyme I had a molecular weight of 600,000-700,000 and enzyme II one of 68,000, as determined on gel filtration. On sodium dodecyl sulfate polyacrylamide slab gel electrophoresis under denaturing conditions, enzyme II gave a single band with a molecular weight of 62,000, while enzyme I gave two minor bands with molecular weights of 32,000 and 20,000 in addition to the major band at 62,000. Both enzymes liberated the terminal galactose from GM1 ganglioside and lactosylceramide but not from galactosylceramide. Enzyme I showed a pH optimum of 4.0 and was heat stable, while enzyme II showed a pH optimum of 5.0 and lost 50% of its activity in 15 min at 45 degrees C. Enzyme I showed a pI of 4.2 and enzyme II one of 5.9.     

Fluorescence-based detection of lacZ reporter gene expression in intact and viable bacteria including Mycobacterium species

A variety of fluorescein di-beta-D-galactopyranoside (FDG)-based substrates were evaluated for measuring beta-galactosidase expression in bacteria. One substrate, 5-acetylamino-FDG (C2FDG), performed well in all bacteria tested, including the slow growing mycobacterium, Mycobacterium bovis BCG. The sensitivity of C2FDG in intact, viable BCG was similar to that of o-nitrophenyl-beta-D-galactopyranoside in cell lysates when used to measure lacZ reporter gene activity. C2FDG was approximately 70-fold more sensitive than green fluorescent protein (GFP) in BCG when assayed in a fluorescence plate reader, and comparable to GFP when measured by flow cytometry. These assays provide an important new alternative for the rapid measurement of reporter gene expression in viable bacteria.     

Purification and some properties of ornithine decarboxylase from rat liver

Ornithine decarboxylase (EC 4.1.1.17) was purified to near homogeniety from livers of thioacetamide- and dl-α-hydrazino-δ-aminovaleric acid-treated rats by using three types of affinity chromatography with pyridoxamine phosphate-Sepharose, pyridoxamine phosphate-dipropylenetriamine-Sepharose and heparin-Sepharose. This procedure gave a purification of about 3.5·10⁵-fold with an 8% yield; the specific activity of the final enzyme preparation was 1,1·10⁶ nmol CO₂/h per mg protein. The purified enzyme gave a single band of protein which coincided with activity peak on polyacrylamide gel electrophoresis and also gave a single major band on SDS-polyacrylamide gel electrophoresis. A single precipitin line was formed between the purified enzyme and an antiserum raised against a partially purified enzyme, on Ouchterlony immunodiffusion. The molecular weight of the enzyme was estimated to be 105 000 by polyacrylamide gel electrophoresis at several different gel concentrations; the dissociated subunits had molecular weights of 50 000 on SDS-polyacrylmide gels. The isoelectric point of the enzyme was pH 4.1.     

Detection of acid-beta-galactosidase activity in viable human fibroblasts by flow cytometry

The fluorogenic substrate fluorescein-di-beta-D-galactopyranoside was used to detect acid beta-galactosidase in intact cultured human fibroblasts. The accumulation of intracellular fluorescein, as measured by flow cytophotometry was linear with the incubation time in three control strains. The two fibroblast strains from patients with acid beta-galactosidase deficiency did not show an accumulation of intracellular fluorescence. Within one control cell population there was a positive correlation between the amount of accumulated intracellular fluorescein fluorescence and the specific acid beta-galactosidase activity as measured biochemically on sorted cells from different zones of the fluorescence distribution. No correlation was found between the specific acid beta-galactosidase activity and the fluorescein fluorescence of three different control cell strains.     

Purification and characterization of fatty acid-binding protein from rat kidney

We detected the presence of a fatty acid-binding protein (FABP) in rat kidney cytosols. This protein was eluted and purified 9.3-fold by sequential gel filtration and anion-exchange chromatography. Homogeneity was shown by a single band on polyacrylamide gel with a molecular weight of about 15,500. It had an optimum binding pH of 7.4. The binding of palmitate to the protein was saturable. Examination of fatty acid binding revealed the presence of a single class of fatty acid-binding sites. The apparent dissociation constant was 1.0 microM and the maximal binding capacity was 48 nmol/mg of protein. This protein showed similar binding characteristics for palmitate, oleate, and arachidonate. Rabbit antibody to this cytosolic FABP gave a single precipitin line with the antigen and selectively inhibited [14C]palmitate binding to the protein.     

Purification and some properties of alkaline pullulanase from a strain of bacillus no. 202-1, an alkalophilic microorganism.

Pullulanase (pullulan 6-glucanohydrolase EC 3.2.1.41) was purified about 290-fold from the culture fluid of Bacillus No. 202-1 by DEAE-cellulose adsorption, acetone fractionation, (NH4) 2SO4 precipitation and DEAE--cellulose column chromatography followed by Sephadex G-200 molecular sieve chromatography. The enzyme gave a single band of protein by disc polyacrylamide gel electrophoresis. The molecular weight was estimated as 92 000 by sodium dodecyl sulfate gel electrophoresis. The isolectric point was lower than pH 2.5. The optimum pH for enzyme action was about 8.5-9.0. The action of the enzyme on amylopectin and glycogen resulted in increase in the iodine coloration of 85% and 70%, respectively. The enzyme completely hydrolyzed 1,6-alpha-glucosidic linkages in amylopectin, glycogen and pullulan.     

Expression of hepatitis B virus surface antigen in adult rat liver. Co-introduction of DNA and nuclear protein by a simplified liposome method.

We established a simple and efficient method for gene transfer in vitro (to cultured cells) and in vivo (to an adult organ) using liposomes. Plasmid DNA and proteins were efficiently co-encapsulated in liposomes by agitation and sonication, and were co-introduced into cells by hemagglutinating virus of Japan (HVJ)-mediated membrane fusion. Introduction of the Escherichia coli beta-galactosidase gene with non-histone chromosomal protein high mobility group 1 (HMG1) into LLCMK2 cells resulted in about 3 times higher beta-galactosidase activity than that on introduction of the gene alone. Two days after injection of HVJ-liposomes containing the beta-galactosidase gene and HMG1 under the perisplanchnic membrane of adult rat liver, hepatic cells near the injection site were found by 5-bromo-4-chloro-3-indolyl beta-D-galactoside staining to have beta-galactosidase activity. After similar injection of HVJ-liposomes containing the hepatitis B virus surface antigen (HBsAg) gene and HMG1, HBsAg was detected in the serum for 9 days with a maximum of 25-45 ng/ml on day 2 after the injection.