[Management of Stent-graft migration with obstruction of supra-aortic vessel during an endovascular procedure for aortic isthmus rupture]

The endovascular approach is widely used in the management of aortic isthmic rupture. Even if it remains less invasive than conventional surgery, a life-threatening complications are possible. We report the case of a young female patient presenting a stent-graft migration during the deployment with total obstruction of the supra-aortic vessels. We describe the therapeutic management with a cerebral rescue procedure followed by a delayed surgical repair.

Effect of testosterone supplementation on nitroso-redox imbalance, cardiac metabolism markers, and S100 proteins expression in the heart of castrated male rats

The aim of this study was to investigate the effects of castration and testosterone supplementation on nitroso-redox status, cardiac metabolism markers, and S100 proteins expression in the heart of male rats. 50 male Wistar rats were randomized into five groups with ten animals each: group 1: control intact (CON); group 2: sham operated (Sh-O); group 3: sesame oil-treated rats (S-oil); group 4: gonadoectomized (GDX); and group 5: gonadoectomized rats treated with testosterone (GDX-T) for 8 weeks. Our results showed myofibrillar weaving, apoptosis, inflammation, and fibrosis (as reflected by increased activity of MMP 9 and MMP 2) in the heart of gonadoectomized rats. Testosterone supplementation restored the normal structure of the heart. In addition, a state of nitroso-redox imbalance was observed in the heart of castrated rats with increased NO (425.1 ± 322.8 vs. 208 ± 67.06, p ˂ 0.05) and MDA (33.18 ± 9.45 vs. 22.04 ± 7.13, p ˂ 0.05) and decreased GSH levels (0.71 ± 0.13 vs. 1.09 ± 0.19, p = 0.001). Testosterone treatment leads to a re-establish of only NO levels (425.1 ± 322.8 vs. 210.4 ± 114.3, p > 0.05). Markers of cardiac metabolism showed an enhancement of LDH activity (12725 ± 4604 vs. 5381 ± 3122, p ˂ 0.05) in the heart of castrated rats. This was inversed by testosterone replacement (12725 ± 4604 vs. 5781 ± 5187, p ˂ 0.05). Furthermore, castration induced heart's accumulation of triglycerides (37.24 ± 6.17 vs. 27.88 ± 6.47, p ˂ 0.05) and total cholesterol (61.44 ± 3.59 vs. 54.11 ± 7.55, p ˂ 0.05), which were significantly reduced by testosterone supplementation (29.03 ± 2.47 vs. 37.24 ± 6.17, p ˂ 0.05) and (47.9 ± 4.15 vs. 61.44 ± 3.59, p ˂ 0.001). Cardiomyocytes of castrated rats showed a decreased immunoexpression of S100 proteins compared to control animals. A restoration of S100 proteins immunostaining in cardiomyocyte cytoplasm was observed after testosterone supplementation. These findings confirm the deleterious effects of testosterone deficiency on cardiac function and highlight the involvement of nitric oxide, metalloproteinases 2 and 9, and S100 proteins.

Use of the Saccharomyces cerevisiae endopolygalacturonase promoter to direct expression in Escherichia coli

In Saccharomyces cerevisiae, an endopolygalacturonase encoded by the PGL1 gene catalyzes the random hydrolysis of the α-1,4 glycosidic linkages in polygalacturonic acid. To study the regulation of the PGL1 gene, we constructed a reporter vector containing the lacZ gene under the control of PGL1 promoter. Surprisingly, when Escherichia coli DH5α was transformed by this vector, cells harboring the constructed plasmid produced blue colonies. Sequence analysis of this promoter revealed that E. coli consensus sequences required to express an in-frame lacZ alpha product were present. We next decided to investigate how the PGL1 promoter is regulated in E. coli compared to yeast. In this study, we examined the modulation of the PGL1 promoter in E. coli, and the results indicated that its activity is greatly induced by saturated digalacturonic acid and is indirectly regulated by the transcriptional regulators the 2-keto-3-deoxygluconate repressor. Moreover, PGL1 expression is enhanced under aerobic conditions. We found that β-galactosidase activity in E. coli could reach 180 units, which is 40-fold greater than the activity produced in S. cerevisiae, and greater than recombinant protein expression previously reported by other researchers. We thus demonstrate that this vector can be considered as a dual expression plasmid for both E. coli and S. cerevisiae hosts. So far, no modulation of endoPG promoters expressed in E. coli has been reported.

Inhibition of chitin synthase by a series of 7-deoxycasuarine stereoisomers designed as constrained analogues of the potent inhibitor 6-deoxyhomoDMDP

A series of polyhydroxy-pyrrolizidines were designed as constrained analogues of 6-deoxy-homoDMDP, a potent naturally occurring inhibitor of chitin synthase. Enzymatic evaluation revealed that 7-deoxycasuarine was the best inhibitor of the series (IC50 = 820 microM) displaying a noncompetitive inhibition pattern, whereas the other tested compounds had IC50 in the range 4.3-18.9 mM. This is the first report of pyrrolizidine-type iminosugars inhibiting a glycosyltransferase. In addition, the inhibitory potencies towards glycosidases of these synthetic casuarine analogues is also disclosed.

Inhibition of chitin synthase by a series of 7-deoxycasuarine stereoisomers designed as constrained analogues of the potent inhibitor 6-deoxyhomoDMDP

A series of polyhydroxy-pyrrolizidines were designed as constrained analogues of 6-deoxyhomoDMDP, a potent naturally occurring inhibitor of chitin synthase. Enzymatic evaluation revealed that 7-deoxycasuarine was the best inhibitor of the series (IC50 = 820 microM) displaying a non-competitive inhibition pattern, whereas the other tested compounds had IC50 in the range 4.3-18.9 mM. This is the first report of pyrrolizidine-type iminosugars inhibiting a glycosyltransferase. In addition, the biological evaluation towards glycosidases of these synthetic casuarine analogues is also disclosed.

Selective and sensitive detection of pectin lyase activity using a colorimetric test: application to the screening of microorganisms possessing pectin lyase activity

Several methods have been described for the detection and quantification of polygalacturonase (PG) and pectin lyase (PL) activities. The most frequently used tests are the Nelson method using copper(II) and an arsenomolybdate reagent to detect PG activity, and the colorimetric method using thiobarbituric acid (TBA) to detect PL activity. We observed that none of these methods are suitable to differentiate between these two enzymatic activities. Therefore, we optimized the test conditions of the TBA method. As a result, the detection of the enzymatic beta-elimination (PL activity) became sensitive and selective. A basic pretreatment at 80 degrees C for 5 min of the solution which contains the pectin fragments of the PL activity furnished aldehydes which were condensed with TBA or its derivatives. After acidification of the medium, a pink fluorescent dye was detected spectrophotochemically (lambda = 550 nm). The interference of galacturonic acid or oligomers resulting from PG activity was completely eliminated. The most sensitive reagent was N-(pyridin-2-yl)-thiobarbituric acid. The application of this method with the new reagent was extended to the screening of microorganisms possessing the PL activity. The obtained results confirm that Aspergillus niger strain and a Saccharomyces cerevisiae SCPP strain possess this activity.

FTIR spectroscopic analysis of Saccharomyces cerevisiae cell walls: study of an anomalous strain exhibiting a pink-colored cell phenotype

A new strain, exhibiting an intriguing pink-colored cell phenotype, was obtained after an encoding alpha-glucosidase gene from an archaebacteria Thermococcus hydrothermalis was cloned by functional complementation of a mal11 Saccharomyces cerevisiae mutant TCY70. The possible implications of the alpha-glucosidase on the cell wall were evaluated by infrared spectroscopy and data indicate a 30% decrease in mannoproteins and an increase in beta-glucans. The loss of mannoproteins was confirmed by experiments on cells deprived of peptidomannans. Modifications in the major components of the cell wall did not jeopardize cell viability. Such rapid optical spectroscopic method can be used to screen a wide range of yeast mutants.

Impact of coronary plaque morphology as assessed by IVUS computer-aided analysis on mechanisms of balloon angioplasty and stenting

This study was performed in order to quantitate structural coronary plaque modifications after balloon angioplasty and stenting and to evaluate the impact of plaque morphology on the mechanisms of lumen enlargement during angioplasty. Plaque morphology was studied by computer-aided analysis of 60 cross-sectional intravascular ultrasound (IVUS) images of the target lesion in 20 patients undergoing percutaneous coronary angioplasty. Based on a computer-aided video densitometry classification of plaque morphology, three groups of plaques were defined based on the slope value of a fifth polynomial regression of the plaque gray-level distribution. In groups A and B, balloon angioplasty provided significant increases in lumen area (P < 0.0001) and vessel area (P < 0.05) without a reduction in plaque area; neither parameter increased in group C. In group A, stenting was associated with an additional lumen enlargement (P < 0.0001) due to plaque reduction (P < 0.05). In groups B and C, stenting further increased lumen area (P < 0.0001) by improving vessel area (P < 0.001) but without plaque reduction. Balloon angioplasty and stenting provided a significant decrease in plaque area in group A as compared to groups B (P < 0.05) and C (P < 0.01). Finally, vessel area improvement was greater in group B than in groups A (P < 0.01) and C (P < 0.05). The mechanisms underlying lumen enlargement after coronary angioplasty are highly dependent on plaque morphology as defined by an IVUS computer-aided analysis and may differ between balloon angioplasty and stenting.

Regulation of the expression of endopolygalacturonase gene PGU1 in Saccharomyces

Previous work in our laboratory has shown that Saccharomyces bayanus strain SCPP is the only reported yeast expressing the three types of pectolytic enzymes: pectin esterases, pectin lyases and polygalacturonases. One of these enzymes, the endopolygalacturonase (endoPG), hydrolyses plant-specific polysaccharide pectin. The endoPG encoding gene (PGU1) is also present in Saccharomyces cerevisiae. It has been shown that this endoPG is required for the development of pseudohyphae. Using genomic DNA, the PGU1-1 and PGU1-2 promoters of these strains have been amplified and used to construct gene fusions with the beta-galactosidase gene. On the basis of beta-galactosidase measurements, we compared the expression of both promoters in different environmental conditions in order to identify their modulation. We have shown that the PGU1 gene is upregulated by the presence of the pectin and the product resulting from endopolygalacturonase activity. Moreover, expression of the PGU1 is also enhanced under respiratory and filament formation conditions.

Genetic reidentification of the pectinolytic yeast strain SCPP as Saccharomyces bayanus var. uvarum

Using genetic hybridization analysis, pulsed-field gel electrophoresis of chromosomal DNA and PCR/RFLP analysis of the MET2 gene, we reidentified 11 Champagne yeast strains. Two of them, SCPP and SC4, were found to belong to Saccharomyces bayanus var. uvarum and the remaining strains to S. cerevisiae. Strain

Kinetics of thermal deactivation of enzymes: a simple three parameters phenomenological model can describe the decay of enzyme activity, irrespectively of the mechanism

Heat induced enzyme inactivation or protein denaturation is now well documented, due to progresses in methods, instruments and computation resources. Complex mechanisms, rather than the classic simple "one step - two states" model (still in use) are recognized in many cases, leading investigators to manipulate more or less complicated kinetic expressions describing the heat induced decay of enzyme activity.We show that the different kinetic expressions related to different mechanisms among the most frequently encountered can be arranged in a common simple three-parameters biexponential equation.This unifying simplification is of interest for people focusing attention to phenomenological rather than mechanistic description of the kinetics of heat induced enzyme deactivation. Moreover, the reduction in the number of parameters reduces the risk of cross-correlation and allows a better estimation of the apparent rate constants (which are in many cases the pertinent required information). It also illustrates the difficulty to make inference of mechanism from kinetics, since the same equation applies for a variety of mechanisms ("kinetic homeomorphism") - in particular, it stresses out the need of caution when reporting on existence of isoenzymes from deactivation kinetics.Application of this simple 3-parameters biexponential kinetic expression has been validated with a number of results in the Literature and current investigations in our laboratory. Two examples are given.

Enhancement of in vitro growth and resistance to gray mould of Vitis vinifera co-cultured with plant growth-promoting rhizobacteria

The potential of a plant growth-promoting rhizobacterium, Pseudomonas sp. (strain PsJN), to stimulate the growth and enhancement of the resistance of grapevine (Vitis vinifera L.) transplants to gray mould caused by Botrytis cinerea has been investigated. In vitro inoculation of grapevine plantlets induced a significant plant growth promotion which made them more hardy and vigorous when compared to non-inoculated plantlets. This ability increased upon transplanting. When grown together with B. cinerea, the causal agent of gray mould, significant differences of aggressiveness were observed between the inoculated and non-inoculated plants. The presence of bacteria was accompanied by an induction of plant resistance to the pathogen. The beneficial effect from this plant-microbe association is being postulated.

Cloning and expression of an alpha-amylase encoding gene from the hyperthermophilic archaebacterium Thermococcus hydrothermalis and biochemical characterisation of the recombinant enzyme

An alpha-amylase encoding gene from the extremely thermophilic Archaea Thermococcus hydrothermalis was cloned and expressed in Escherichia coli. The encoded alpha-amylase possesses molecular characteristics specific to the Archaea, especially from Pyrococcus species, with biochemical characteristics of the alpha-amylases from Thermococcus. The gene is 1374 bp long and encodes a protein of 457 amino acids composed of a 22 amino acid putative signal peptide and a 435 amino acid mature protein (calculated molecular mass 49236 Da). The T. hydrothermalis recombinant alpha-amylase is optimally active at 75-85 degrees C and at pH 5.0-5.5.

Physiologically guided angioplasty in support to a provisional stenting strategy: immediate and six-month outcome

The results of an observational multicenter angioplasty study suggested that stenting decisions may be facilitated by physiologic data. The purpose of this study was to evaluate the early and long-term clinical and angiographic outcome of prospective physiologically guided provisional stenting. Coronary angioplasty using a Doppler-tipped angioplasty guidewire was performed in 68 patients. The provisional stent strategy dictated that balloon angioplasty was to be continued until a coronary flow reserve was >/= 2.2 with a residual diameter stenosis by quantitative coronary angiography < 35%. Repeat coronary angiography was obtained at 6 months. Based on the study criteria, 32/68 patients (47%) received a stent. Compared to the stent group, the angioplasty alone group had higher postprocedural stenosis (23% +/- 13% vs. 13% +/- 10%; P < 0. 05) and lower coronary vasodilatory reserve (2.3 +/- 0.4 vs. 2.6 +/- 0.7; P < 0.05). At follow-up (6.0 +/- 1.5 months), the angiographic restenosis rate was 39% in the angioplasty group and 35% in the stent groups (P = NS). Adverse cardiac events (unstable angina, target lesion revascularization, myocardial infarction, death) occurred in 19% and 18% (P = NS) of the angioplasty and stent patients, respectively. A prospective application of a physiologically guided provisional stent strategy for coronary angioplasty indicated that stent implantation may be required in approximately 50% of patients, an approach that produces similar clinical and angiographic long-term outcomes for stenting and guided angioplasty. These data support a role of coronary physiology as an adjunct in conducting an angioplasty procedure without obligatory stenting.

Purification and characterization of acidic endo-polygalacturonase encoded by the PGL1-1 gene from Saccharomyces cerevisiae

The PGL1 gene of the yeast Saccharomyces cerevisiae has been shown to encode polygalacturonase. Cloning of the PGL1 open reading frame behind the ADH1 promoter allowed overexpression of polygalacturonase activity in S. cerevisiae. This enzyme was purified to apparent homogeneity from cultures of recombinant S. cerevisiae on synthetic medium using one-step purification by anionic exchange chromatography. The enzyme, named Pgl1P, had an apparent M(r) of 42 kDa as shown by SDS-PAGE. Pgl1P was active from pH 3 to 5.5, with an optimum temperature at 25 degrees C. This enzyme hydrolyzed polygalacturonic acid as an endo-polygalacturonase as demonstrated by independent methods. The purified protein was N-glycosylated. However, the activity remained in the N-deglycosylated form. The N-terminal amino acid sequence was also determined as D-S-C-T-L-T-G-S-S-L.

[Aortic dissection at 6 months gestation in a women with Marfan's syndrome. Simultaneous Bentall intervention and cesarean section]

A 31 year old woman with Marfan's syndrome had a dilatation of the aortic root (55-60 mm at the beginning of pregnancy). Pregnancy was continued with beta-blocker therapy and with regular echocardiographic follow-up. The aortic dilatation increased (62-65 mm) at the last control and, at the 34th week of pregnancy, the patient suffered a dissection of the ascending aorta. A caesarean section was performed with a Bentall procedure during the same operative session. The mother and baby girl are well two years later. The problems of pregnancy in patients with Marfan's syndrome are discussed.

Cloning of an alpha-glucosidase gene from Thermococcus hydrothermalis by functional complementation of a Saccharomyces cerevisiae mal11 mutant strain

alpha-Glucosidase is found in methanogenic and thermophilic archaea and also in eukaryotes and bacteria. The gene encoding the enzyme was cloned from Thermococcus hydrothermalis by complementation of a Saccharomyces cerevisiae deficiency maltase mutant strain. The gDNA clone isolated encodes an open reading frame corresponding to a protein of 242 amino acids. The protein shows 42% identity to a Pyrococcus horikoshii unknown ORF but no similarities were obtained with polysaccharidase sequences.

Close evolutionary relatedness of alpha-amylases from Archaea and plants

The amino acid sequences of 22 alpha-amylases from family 13 of glycosyl hydrolases were analyzed with the aim of revealing the evolutionary relationships between the archaeal alpha-amylases and their eubacterial and eukaryotic counterparts. Two evolutionary distance trees were constructed: (i) the first one based on the alignment of extracted best-conserved sequence regions (58 residues) comprising beta2, beta3, beta4, beta5, beta7, and beta8 strand segments of the catalytic (alpha/beta)8-barrel and a short conserved stretch in domain B protruding out of the barrel in the beta3 --> alpha3 loop, and (ii) the second one based on the alignment of the substantial continuous part of the (alpha/beta)8-barrel involving the entire domain B (consensus length: 386 residues). With regard to archaeal alpha-amylases, both trees compared brought, in fact, the same results; i.e., all family 13 alpha-amylases from domain Archaea were clustered with barley pI isozymes, which represent all plant alpha-amylases. The enzymes from Bacillus licheniformis and Escherichia coli, representing liquefying and cytoplasmic alpha-amylases, respectively, seem to be the further closest relatives to archaeal alpha-amylases. This evolutionary relatedness clearly reflects the discussed similarities in the amino acid sequences of these alpha-amylases, especially in the best-conserved sequence regions. Since the results for alpha-amylases belonging to all three domains (Eucarya, Eubacteria, Archaea) offered by both evolutionary trees are very similar, it is proposed that the investigated conserved sequence regions may indeed constitute the "sequence fingerprints" of a given alpha-amylase.

[Intra-coronary ultrasonography during angioplastic procedures]

Thanks to miniaturization and constant improvement of technologies, intracoronary ultrasound (ICUS) progressively takes its place as the best tool to accurately analyze arterial wall structure. However, its routine use during interventional procedures remains limited. ICUS provides precious informations, complementary to angiography, and guide interventional procedures on the basis of a more accurate analyze of the components of the plaque, thus improving their success rate. Since its use favorized the understanding of the different devices mechanisms (angioplasty, stents, directional and rotational atherectomy), ICUS contributed to reduce the incidence of their complications. Many studies have emphasized ICUS interest during these procedures: their results seem to be significantly improved by the way of prompting the operator to adopt an aggressive strategy (additional inflations using high pressures, combination of different techniques...) which tend to reduce the complication rate and the restenosis incidence. Actually, the restenosis rate was in all these studies [OARS (29%), ABACAS (21%) and MUSIC (8.3%)] directly associated to ICUS parameters measured immediately after treatment, particularly the residual plaque burden. Whether its use, that engender substantial cost, cannot be systematic, trained centers will probably demonstrate that a rational and suitable use lead to adopt optimal strategies and achieve improved results.

Cloning, sequence analysis and overexpression of a Saccharomyces cerevisiae endopolygalacturonase-encoding gene (PGL1)

Only a few yeast strains produce pectin-degrading enzymes such as pectin esterases and depolymerases (hydrolases and lyases). Strain SCPP is the only known Saccharomyces strain to produce these pectinases. One of these pectolytic enzymes. PGL1-encoded endopolygalacturonase (EC 3.2.1.15), hydrolyses the alpha-1,4-glycosidic bonds within the rhamnogalacturonan chains in pectic substances. This paper presents the cloning and sequencing of the first S. cerevisiae gene involved in pectin degradation. Few differences were found between the two deduced amino acid sequences encoded by PGL1-1 from a pectolytic (PG+) strain (SCPP) and PGL1-2 from a non-pectolytic (PG-) strain (X2180-1B). Similarities were found with other polygalacturonases from plants and other microorganisms. Of the two S. cerevisiae genes, only the one isolated from strain SCPP was able, by overexpression, to confer endopolygalacturonase activity to a laboratory strain of S. cerevisiae. Overexpression of PGL1-1 gene in a non-pectolytic strain resulted in halo formation on polygalacturonic acid-containing agar plates stained with ruthenium red.

Detection method for polygalacturonase-producing strains of Saccharomyces cerevisiae

In the presence of glycerol or ethanol, SCPP (a strain of Saccharomyces cerevisiae that expresses pectinolytic activity) is capable of utilizing galacturonic acid or pectins for growth purposes. We now establish a relationship between the pectinolytic power of various strains of S. cerevisiae and their ability to grow on a pectin/glycerol-based medium. This property is further exploited for the detection of polygalacturonase-producing strains of S. cerevisiae.

[15 years of coronary angioplasty: focus on the different techniques]

The growth of transcutaneous coronary angioplasty in the 1980s and early 1990s was particularly rapid, as about 42,000 procedures were performed in France in 1994. This treatment for coronary atherosclerosis now constitutes a valid alternative to surgical or medical treatment. New treatment modalities for coronary atherosclerosis have been added to the original balloon technique. Two types of coronary angioplasty can now be performed depending either by flattening and crushing the atheroma against the arterial wall (balloon, stent) or by destroying and fragmenting it (Rotablator, Laser, directional atherectomy). Among these new instruments, vascular stents have reduced the incidence of restenosis and have improved the safety of interventional cardiology, while others, such as Rotablator and Laser, allow the treatment of lesions inaccessible to the balloon. Directional atherectomy, by allowing specific excision, will occupy an important place in future developments of interventional cardiology, which is still a relatively young specialty.

Detection of polygalacturonase, pectin-lyase and pectin-esterase activities in a Saccharomyces cerevisiae strain

The catalytic capacity of several excreted pectinolytic enzymes obtained from various yeast strains was examined using in vivo and biochemical techniques. Of the 33 yeast strains studied, 30 were isolated from champagne wine during alcoholic fermentation. Only one yeast strain was found to excrete pectinolytic enzymes and was identified as Saccharomyces cerevisiae and designated SCPP. Pulsed-field gel electrophoresis and the polymerase chain reaction technique were used to characterize further this specific strain. Three types of pectinolytic enzymes were found to be excreted by SCPP: polygalacturonase, pectin-lyase and pectin-esterase. These enzymes allow pectin hydrolysis during cell growth.

Cloning and structure of the pyrE gene of Lactobacillus plantarum CCM 1904

The pyrE gene of Lactobacillus plantarum CCM 1904, coding for the orotate phosphoribosyl transferase involved in the pyrimidine biosynthetic pathway, was cloned in Escherichia coli and sequenced. The predicted polypeptide sequence extending over 212 amino acids (MW 22,690) was compared to those of E. coli and to those of lower eukaryotes (Saccharomyces cerevisiae, Podospora anserina, Sordaria macrospora, Dictyostelium discoideum). Important conserved stretches were revealed, implying that these proteins are closely related.

Structural organization of pLP1, a cryptic plasmid from Lactobacillus plantarum CCM 1904

To construct shuttle vectors based on an endogenous replicon, we isolated a small cryptic plasmid (pLP1) from Lactobacillus plantarum CCM 1904. The nucleotide sequence (2093 bp, 38.25 GC mol%) revealed one major open reading frame encoding for a 317 amino acid protein (Rep). Comparisons with proteins encoded by other Gram-positive bacteria plasmids strongly suggest that the protein encoded by pLP1 has a replicative role. The presence of a consensus sequence including a tyrosine residue known to be the replication protein binding site to the DNA (in phage phi X174) strengthens this hypothesis. The DNA sequence contains also a sequence similar to the pC194 origin nick sequence, which initiates the plasmid replication at the plus origin, characteristic of plasmids which replicate following a rolling circle mechanism via single-stranded DNA intermediates. A set of 13 direct repeats of 17 bp could be involved in the expression of the incompatibility or in the copy number control as in the other plasmids. A promoter sequence located at the rep 5' region has been identified and is functional in Bacillus subtilis.

Cloning and analysis of the gene for the major outer membrane lipoprotein from Pseudomonas aeruginosa

The gene for the Pseudomonas aeruginosa outer membrane lipoprotein I was isolated from a genomic library in the phage lambda EMBL3 vector and subsequently subcloned in the low copy-number, wide host-range plasmid vector, pKT240. The cloned gene was highly expressed, resulting in the production of a low molecular-weight protein (8 kD) that was found to be associated with the outer membrane. Sequence analysis showed an open reading frame of 83 amino acids with a putative N-terminal hydrophobic signal peptide of 19 residues immediately followed by the lipoprotein consensus sequence, GLY-CYS-SER-SER (residues 19-22). The predicted amino acid composition of the mature polypeptide and that of the purified lipoprotein I of P. aeruginosa (Mizuno and Kageyama, 1979) were identical. In contrast with other Gram-negative outer membrane lipoproteins, conformation predictions suggested that the mature protein was a single alpha helix.

Structure and expression of the URA5 gene of Saccharomyces cerevisiae

The URA5 gene of Saccharomyces cerevisiae encodes orotate phosphoribosyl transferase (EC 2.4.2.10; OPRTase) which catalyses the transformation of orotate to OMP in the pyrimidine pathway. We present in this paper the cloning and the sequencing of this gene, the last in the yeast pyrimidine pathway to be cloned. We have deduced the protein sequence of the OPRTase of S. cerevisiae from the DNA sequence and compared it to that of Escherichia coli, Podospora anserina and Dictyostelium discoideum. Some important similarities in the structure of these four proteins have been found. Finally, we have quantified the transcription of the URA5 gene in different physiological conditions and confirmed that it was not under the control of UTP or any intermediary product of the pathway.

Studies on the different molecular forms of tyrosine aminotransferase from rat liver and hepatoma cells

In an attempt to clarify the significance of the separable forms of tyrosine aminotransferase, the enzyme from rat liver and from cultured hepatoma cells was studied by carboxymethyl-Sephadex chromatography. Our studies of the form conversion during the purification procedure of the enzyme, where all cellular components were quickly discarded, do not allow us to invoke a specific "converting factor", the existence of which in the particulate fraction has been suggested. Moreover the addition of serine protease inhibitors is not sufficient to prevent the classical conversion. More probably, several factors depending on the environmental conditions might influence different reactions which lead to a preferential conformation of the enzyme in vitro. The difference in the PO4- content of the various enzyme forms and the consecutive differences in negative charge may be the determining factor in the elution pattern of the three forms of the isolated soluble enzyme. This observation raises the possibility that phosphorylation might play a specific role in the regulation of tyrosine aminotransferase synthesis.