Expanding the scope of methylation-sensitive restriction enzyme (MSRE) PCR for forensic identification of body fluids through the novel use of methylation-dependent restriction enzymes (MDRE) and the combination of autosomal and Y-chromosomal markers

Methylation-sensitive/-dependent restriction enzyme (MSRE/MDRE) PCR can be performed to detect hypomethylated or hypermethylated CpG sites. With the combined use of different tissue-specific CpG markers, MSRE/MDRE-PCR leads to tissue-specific methylation patterns (TSMPs), enabling the correlation of DNA samples to their source tissue. MSRE/MDRE assays can use the same platform as forensic STR typing and offer many advantages in the field of forensic body fluid detection. In the present study, we aimed to establish MSRE assays for the detection of blood, saliva, vaginal secretion, and semen, using markers from literature and from our own database search. We designed two different MSRE test-sets, which include two novel Y-chromosomal non-semen markers, and enable differentiation between female and male non-semen samples. Furthermore, we established an MSRE/MDRE semen approach, which includes only Y-chromosomal non-semen and semen markers. This Y-semen multiplex PCR utilizes the novel combination of the methylation-sensitive enzyme SmaI and the methylation-dependent enzyme GlaI, which enables more sensitive detection of male body fluids within male/female DNA mixtures. Our validation tests confirmed that MSRE/MDRE assays exhibit high sensitivity, similar to that of STR typing.

Comparative NMR analysis of an 80-residue G protein-coupled receptor fragment in two membrane mimetic environments

Fragments of integral membrane proteins have been used to study the physical chemical properties of regions of transporters and receptors. Ste2p(G31-T110) is an 80-residue polypeptide which contains a portion of the N-terminal domain, transmembrane domain 1 (TM1), intracellular loop 1, TM2 and part of extracellular loop 1 of the α-factor receptor (Ste2p) from Saccharomyces cerevisiae. The structure of this peptide was previously determined to form a helical hairpin in lyso-palmitoylphosphatidyl-glycerol micelles (LPPG) [1]. Herein, we perform a systematic comparison of the structure of this protein fragment in micelles and trifluoroethanol (TFE):water in order to understand whether spectra recorded in organic:aqueous medium can facilitate the structure determination in a micellar environment. Using uniformly labeled peptide and peptide selectively protonated on Ile, Val and Leu methyl groups in a perdeuterated background and a broad set of 3D NMR experiments we assigned 89% of the observable atoms. NOEs and chemical shift analysis were used to define the helical regions of the fragment. Together with constraints from paramagnetic spin labeling, NOEs were used to calculate a transiently folded helical hairpin structure for this peptide in TFE:water. Correlation of chemical shifts was insufficient to transfer assignments from TFE:water to LPPG spectra in the absence of further information.

Open adhesiolysis is more effective in reducing adhesion reformation than laparoscopic adhesiolysis in an experimental model

BACKGROUND

This study compared adhesion reformation after open and laparoscopic adhesiolysis in a rat model.

METHODS

Adhesions were induced by surgically creating ischaemic buttons on the peritoneal side wall. After 7 days the animals underwent laparoscopy with carbon dioxide insufflation or laparotomy to score and lyse adhesions. Peritoneal tissue and fluid were collected after 24 h in a subset of animals, and adhesion reformation was scored 7 days after lysis in the remainder. Tissue plasminogen activator (tPA), plasminogen activator inhibitor (PAI) 1, transforming growth factor (TGF) beta1 and tumour necrosis factor (TNF) alpha mRNA, and total fibrinolytic activity were assessed. The abdomen of non-operated animals was insufflated for 7, 15 or 30 min with carbon dioxide, after which tPA and PAI-1 mRNA and total fibrinolytic activity were measured.

RESULTS

Animals that underwent open adhesiolysis had 60 per cent fewer reformed adhesions than the laparoscopic adhesiolysis group (P < 0.001). There were no differences in tPA activity or tPA, PAI-1 and TNF-alpha mRNA between groups, but TGF-beta1 mRNA levels were significantly increased in the open group. Carbon dioxide insufflation did not affect peritoneal tPA activity.

CONCLUSION

Open adhesiolysis may be more beneficial in minimizing adhesion reformation in the management of adhesion-related complications.

A neurokinin 1 receptor antagonist decreases adhesion reformation after laparoscopic lysis of adhesions in a rat model of adhesion formation

BACKGROUND

Up to 94% of patients experience fibrous adhesions after abdominal surgery, and a significant number of these patients require a second operation for open or laparoscopic lysis of adhesions (LOA). The authors have previously shown that inhibition of the binding of tachykinin ligands to the neurokinin 1 receptor (NK-1R) using the neurokinin 1 receptor antagonist (NK-1RA) CJ-12,255 decreases primary adhesion formation and upregulates the peritoneal fibrinolytic system in a rat model. Whereas most studies have focused on the prevention of primary adhesions, few have addressed adhesion reformation after LOA. This study aimed to determine the effects of NK-1RA administration on adhesion reformation and peritoneal fibrinolytic activity after laparoscopic LOA.

METHODS

Adhesions were induced in 31 rats using our previously described ischemic button model. The rats underwent laparoscopy 7 days later, during which adhesions were scored and lysed followed by administration of the NK-1RA or saline. Then 7 days after LOA, 23 rats were killed and adhesions were scored. Eight rats also were killed 24 h after the LOA to obtain peritoneal tissue and fluid, which were analyzed for tissue plasminogen activator (tPA) mRNA expression and peritoneal fibrinolytic activity by reverse transcriptase-polymerase chain reaction (RT-PCR) and bioassay, respectively.

RESULTS

At laparoscopy, 79% +/- 3% of the buttons formed adhesions. In the saline-administered control animals, 42% +/- 3.2% of the buttons reformed adhesions after LOA (p < 0.05), whereas in the animals that received the NK-1RA, 18.2% +/- 3.5% of the buttons reformed adhesions (p < 0.05). As compared with control animals, NK-1RA administration increased tPA mRNA levels by 38% and fibrinolytic activity sixfold (p < 0.05; 7.0 +/- 2.1 U/ml vs 1.2 +/- 0.54 U/ml).

CONCLUSIONS

When administered during laparoscopic LOA, an NK-1RA significantly upregulates peritoneal fibrinolytic activity and decreases adhesion reformation.

ThPTR2, a di/tri-peptide transporter gene from Trichoderma harzianum

The generation of a wide ESTs library and database from Trichoderma harzianum CECT 2413 was the base for identifying the gene ThPTR2, coding for a PTR family di/tri-peptide transporter. The deduced protein sequence of the ThPTR2 gene showed the conserved motifs and also the 12 transmembrane domains typical of the PTR transporters. The highest level of ThPTR2 expression was found when the fungus was grown in chitin as sole carbon source. We also found that ThPTR2 expression was increased when Trichoderma interacted directly in solid medium with the plant-pathogenic fungus Botrytis cinerea, showing that ThPTR2 is involved in the mycoparasitic process. Additionally, its expression was triggered by nitrogen starvation and a higher level of expression was also found when Trichoderma was grown in secondary nitrogen sources like allantoin, yeast extract, and urea. However, no difference was found when Trichoderma was grown in presence or absence of glucose as carbon source. Strain T34-15, a transformant that overexpressed the ThPTR2 gene, showed about a 2-fold increase in the uptake of the dipeptide Leu-Leu. Additionally, two transformants from the strain Trichoderma longibrachiatum T52 that overexpressed ThPTR2 were also studied, confirming the role of this gene in peptide transport. Other homologous genes to ThPTR2 were identified in other Trichoderma strains. ThPTR2 is the first experimentally confirmed PTR family transporter gene from filamentous fungi.

Analysis of ligand-receptor cross-linked fragments by mass spectrometry*

G-protein coupled receptors (GPCRs) are a class of integral membrane receptor proteins that are characterized by a signature seven-transmembrane (7-TM) configuration. The alpha-factor receptor (Ste2p) from Saccharomyces cerevisiae is a GPCR that, upon binding of a peptide ligand, transduces a signal to initiate a cascade of events leading to the mating of haploid yeast cells. This study summarizes the application of affinity purification and of matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) experiments using biotinylated photoactivatable alpha-factor analogs. Affinity purification and enrichment of biotinylated peptides by monomeric avidin beads resulted in mass spectrometric detection of specific signals corresponding to cross-linked fragments of Ste2p. Data obtained from cyanogen bromide (CNBr) fragments of receptor cross-linked to an alpha-factor analog with the photoaffinity group p-benzoyl-l-phenylalanine on position 1 were in agreement with the previous results reported by our laboratory suggesting the cross-linking between position 1 of alpha-factor and a region of Ste2p covering residues 251-294.

Response of winter birds to soil remediation along the Columbia River at the Hanford Site

The Columbia River at the Hanford Site, located in south-central Washington State, U.S.A., is a regionally important refugium for overwintering birds. Some of the river shoreline has been designated by the U.S. Department of Energy for environmental clean-up following past production of materials for nuclear weapons. We evaluated the effects of soil remediation on winter birds at six inactive nuclear reactor areas. Remediation activities consisted of daily excavation and removal of approximately 1035 t of contaminated soil from previously herbicided and denuded areas located between 30 and 400 m and mostly in line-of-sight of the river shoreline. Remediation activities had no apparent effect on numbers of riverine or terrestrial birds using adjacent undisturbed shoreline and riparian habitat.

Peptide fragments as models to study the structure of a G-protein coupled receptor: the alpha-factor receptor of Saccharomyces cerevisiae

The alpha-factor tridecapeptide initiates mating in Saccharomyces cerevisiae upon interaction with Ste2p, its cognate G-protein coupled receptor (GPCR). This interaction is being used as a paradigm for understanding the structure and mechanism of activation of GPCRs by medium-sized peptides. In this article, the use of fragments of Ste2p to study its structure is reviewed. Methods of synthesis of peptides corresponding to both extramembranous and transmembrane domains of Ste2p are evaluated and problems that are encountered during synthesis and purification are described. The results from conformational analyses of the peptide fragments using fluorescence spectroscopy, CD, infrared spectroscopy, and NMR spectroscopy in organic-aqueous mixtures and in the presence of detergent micelles and lipid bilayers are critically reviewed. The data obtained to date provide biophysical evidence for the structure of different domains of Ste2p and indicate that peptides corresponding to these domains have unique biophysical tendencies. The studies carried out on Ste2p fragments indicate that valuable information concerning the structure of the intact receptor can be obtained by studying peptide fragments corresponding to domains of these polytopic integral membrane proteins.

Study of the binding environment of alpha-factor in its G protein-coupled receptor using fluorescence spectroscopy

Mating in Saccharomyces cerevisiae is induced by the interaction of alpha-factor (W1H2W3L4Q5L6K7P8G9Q10P11M12Y13) with its cognate G protein-coupled receptor (Ste2p). Fifteen fluorescently labeled analogs of alpha-factor in which the 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) group was placed at the alphaN-terminus and in side-chains at positions 1, 3, 4, 6, 7, 12 and 13 were synthesized and assayed for biological activity and receptor affinity. Eleven of the analogs retained 6-60% of the biological activity of the alpha-factor, as judged using a growth arrest assay. The binding affinities depended on the position of NBD attachment in the peptide and the distance of the tag from the backbone. Derivatization of the positions 3 and 7 side-chains with the NBD group resulted in analogs with affinities of 17-35% compared with that of alpha-factor. None of the other NBD-containing agonists had sufficient receptor affinity or strong enough emission for fluorescence analysis. The position 3 and 7 analogs were investigated using fluorescence spectroscopy and collisional quenching by KI in the presence of Ste2p in yeast membranes. The results showed that the lambda max of NBD in the position 7 side-chain shifted markedly to the blue (510 nm) when separated by 4 or 6 bonds from the peptide backbone and that this probe was shielded from quenching by KI. In contrast, separation by 3, 5, 10 or more bonds resulted in lambda max ( approximately 540 nm) and collisional quenching constants consistent with increasing degrees of exposure. The NBD group in the position 3 side-chain was also found to be blue shifted (lambda max=520 nm) and shielded from solvent. These results indicate that the position 7 side-chain is likely interacting with a pocket formed by extracellular domains of Ste2p, whereas the side-chain of Trp3 is in a hydrophobic pocket possibly within the transmembrane region of the receptor.

WdChs2p, a class I chitin synthase, together with WdChs3p (class III) contributes to virulence in Wangiella (Exophiala) dermatitidis

The chitin synthase structural gene WdCHS2 was isolated by screening a subgenomic DNA library of Wangiella dermatitidis by using a 0.6-kb PCR product of the gene as a probe. The nucleotide sequence revealed a 2,784-bp open reading frame, which encoded 928 amino acids, with a 59-bp intron near its 5' end. Derived protein sequences showed highest amino acid identities with those derived from the CiCHS1 gene of Coccidioides immitis and the AnCHSC gene of Aspergillus nidulans. The derived sequence also indicated that WdChs2p is an orthologous enzyme of Chs1p of Saccharomyces cerevisiae, which defines the class I chitin synthases. Disruptions of WdCHS2 produced strains that showed no obvious morphological defects in yeast vegetative growth or in ability to carry out polymorphic transitions from yeast cells to hyphae or to isotropic forms. However, assays showed that membranes of wdchs2Delta mutants were drastically reduced in chitin synthase activity. Other assays of membranes from a wdchs1Deltawdchs3Deltawdchs4Delta triple mutant showed that their residual chitin synthase activity was extremely sensitive to trypsin activation and was responsible for the majority of zymogenic activity. Although no loss of virulence was detected when wdchs2Delta strains were tested in a mouse model of acute infection, wdchs2Deltawdchs3Delta disruptants were considerably less virulent in the same model, even though wdchs3Delta strains also had previously shown no loss of virulence. This virulence attenuation in the wdchs2Deltawdchs3Delta mutants was similarly documented in a limited fashion in more-sensitive cyclophosphamide-induced immunocompromised mice. The importance of WdChs2p and WdChs3p to the virulence of W. dermatitidis was then confirmed by reconstituting virulence in the double mutant by the reintroduction of either WdCHS2 or WdCHS3 into the wdchs2Deltawdchs3Delta mutant background.

Identification of residues of the Saccharomyces cerevisiae G protein-coupled receptor contributing to alpha-factor pheromone binding

The Saccharomyces cerevisiae pheromone, alpha-factor (WHWLQLKPGQPMY), and Ste2p, its G protein-coupled receptor, were studied as a model for peptide ligand-receptor interaction. The affinities and activities of various synthetic position-10 alpha-factor analogs with Ste2p expressing mutations at residues Ser47 and Thr48 were investigated. All mutant receptors were expressed at a similar level in the cytoplasmic membrane, and their efficacies of signal transduction were similar to that of the wild-type receptor. Mutant receptors differed in binding affinity (Kd) and potency (EC50) for gene induction by alpha-factor. One mutant receptor (S47K,T48K) had dramatically reduced affinity and activity for [Lys10]- and [Orn10]alpha-factor, whereas the affinity for Saccharomyces kluyveri alpha-factor (WHWLSFSKGEPMY) was increased over 20-fold compared with that of wild-type receptor. In contrast, the affinity of [Lys10]- and [Orn10]alpha-factor was increased greatly in a S47E,T48E mutant receptor, whereas the binding of the S. kluyveri alpha-factor was abolished. The affinity of [Lys10]- and [Orn10]alpha-factor for the S47E,T48E receptor dropped 4-6-fold in the presence of 1 m NaCl, whereas the affinity of alpha-factor was not affected by this treatment. These results demonstrate that when bound to its receptor the 10th residue (Gln) of the S. cerevisiae alpha-factor is adjacent to Ser47 and Thr48 residues in the receptor and that the 10th residue of alpha-factors from two Saccharomyces species is responsible for the ligand selectivity to their cognate receptors. Based on these data, we have developed a two-dimensional model of alpha-factor binding to its receptor.

Structure and topology of a peptide segment of the 6th transmembrane domain of the Saccharomyces cerevisae alpha-factor receptor in phospholipid bilayers

A detailed analysis of the structure of an 18-residue peptide AQSLLVPSIIFILAYSLK [M6(252-269, C252A)] in 1,2-dimyristoyl-sn-glycero-phosphocholine bilayers was carried out using solid state NMR and attenuated total reflection Fourier transform infrared spectroscopy. The peptide corresponds to a portion of the 6th transmembrane domain of the alpha-factor receptor of Saccharomyces cerevisiae. Ten homologs of M6(252-269, C252A) were synthesized in which individual residues were labeled with (15)N. One- and two-dimensional solid state NMR experiments were used to determine the chemical shifts and (1)H-(15)N dipolar coupling constants for the (15)N-labeled peptides in oriented dimyristoylphosphatidylcholine bilayers on stacked glass plates. These parameters were used to calculate the structure and orientation of M6(252-269, C252A) in the bilayers. The results indicate that the carboxyl terminal residues (9-14) are alpha-helical and oriented with an angle of about 8 degrees with respect to the bilayer normal. Independently, an attenuated total reflection Fourier transform infrared spectroscopy analysis on M6(252-269, C252A) in a 1,2-dimyristoyl-sn-glycero-phosphocholine bilayer concluded that the helix tilt angle was about 12.5 degrees. The results on the structure of M6(252-269, C252A) in bilayers are in good agreement with the structure determined in trifluoroethanol/water solutions (B. Arshava et al. Biopolymers, 1998, Vol. 46, pp. 343-357). The present study shows that solid state NMR spectroscopy can provide high resolution information on the structure of transmembrane domains of a G protein-coupled receptor.

ATR-FTIR study of the structure and orientation of transmembrane domains of the Saccharomyces cerevisiae alpha-mating factor receptor in phospholipids

The structures of seven synthetic transmembrane domains (TMDs) of the alpha-factor receptor (Ste2p) from Saccharomyces cerevisiae were studied in phospholipid multilayers by transmission Fourier transform infrared (FTIR) and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopies. Peptide conformation assumed in multilayers depended on the method of sample preparation. Amide proton H/D exchange experiments showed that 60-80% of the NH bonds in these TMDs did not exchange with bulk water in 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) multilayers. FTIR results showed that peptides corresponding to TMDs one, two, and seven were mostly alpha-helical in DMPC multilayers. Peptides corresponding to TMDs three and six assumed predominantly beta-sheet structures, whereas those corresponding to TMDs four and five were a mixture of alpha-helices and beta-sheets. ATR-FTIR showed that in DMPC the alpha-helices of TMDs two and five oriented with tilt angles of 34 degrees and 32 degrees, respectively, with respect to the multilayer normal. Similar results were obtained for six of the transmembrane domains in DMPC/DMPG (4:1) multilayers. In a mixture [POPC/POPE/POPS/PI/ergosterol (30:20:5:20:25)] which mimicked the lipid composition of the S. cerevisiae cell membrane, the percentage of alpha-helical structures found for TMDs one and five increased compared to those in DMPC and DMPC/DMPG (4:1) multilayers, and TMD six exhibited a mixture of beta-sheet ( approximately 60%) and alpha-helical ( approximately 40%) structure. These experiments provide biophysical evidence that peptides representing the seven transmembrane domains in Ste2p assume different structures and tilt angles within a membrane multilayer.

Molecular cloning and characterization of WdPKS1, a gene involved in dihydroxynaphthalene melanin biosynthesis and virulence in Wangiella (Exophiala) dermatitidis

1,8-Dihydroxynaphthalene (1,8-DHN) is a fungal polyketide that contributes to virulence when polymerized to 1,8-DHN melanin in the cell walls of Wangiella dermatitidis, an agent of phaeohyphomycosis in humans. To begin a genetic analysis of the initial synthetic steps leading to 1,8-DHN melanin biosynthesis, a 772-bp PCR product was amplified from genomic DNA using primers based on conserved regions of fungal polyketide synthases (Pks) known to produce the first cyclized 1,8-DHN-melanin pathway intermediate, 1,3,6,8-tetrahydroxynaphthalene. The cloned PCR product was then used as a targeting sequence to disrupt the putative polyketide synthase gene, WdPKS1, in W. dermatitidis. The resulting wdpks1Delta disruptants showed no morphological defects other than an albino phenotype and grew at the same rate as their black wild-type parent. Using a marker rescue approach, the intact WdPKS1 gene was then successfully recovered from two plasmids. The WdPKS1 gene was also isolated independently by complementation of the mel3 mutation in an albino mutant of W. dermatitidis using a cosmid library. Sequence analysis substantiated that WdPKS1 encoded a putative polyketide synthase (WdPks1p) in a single open reading frame consisting of three exons separated by two short introns. This conclusion was supported by the identification of highly conserved Pks domains for a beta-ketoacyl synthase, an acetyl-malonyl transferase, two acyl carrier proteins, and a thioesterase in the deduced amino acid sequence. Studies using a neutrophil killing assay and a mouse acute-infection model confirmed that all wdpks1Delta strains were less resistant to killing and less virulent, respectively, than their wild-type parent. Reconstitution of 1,8-DHN melanin biosynthesis in a wdpks1Delta strain reestablished its resistance to killing by neutrophils and its ability to cause fatal mouse infections.

Chs1 of Candida albicans is an essential chitin synthase required for synthesis of the septum and for cell integrity

CaCHS1 of the fungal pathogen Candida albicans encodes an essential chitin synthase that is required for septum formation, viability, cell shape and integrity. The CaCHS1 gene was inactivated by first disrupting one allele using the ura-blaster protocol, then placing the remaining allele under the control of the maltose-inducible, glucose-repressible MRP1 promoter. Under repressing conditions, yeast cell growth continued temporarily, but daughter buds failed to detach from parents, resulting in septumless chains of cells with constrictions defining contiguous compartments. After several generations, a proportion of the distal compartments lysed. The conditional Deltachs1 mutant also failed to form primary septa in hyphae; after several generations, growth stopped, and hyphae developed swollen balloon-like features or lysed at one of a number of sites including the hyphal apex and other locations that would not normally be associated with septum formation. CHS1 therefore synthesizes the septum of both yeast and hyphae and also maintains the integrity of the lateral cell wall. The conditional mutant was avirulent under repressing conditions in an experimental model of systemic infection. Because this gene is essential in vitro and in vivo and is not present in humans, it represents an attractive target for the development of antifungal compounds.

Probing the binding domain of the Saccharomyces cerevisiae alpha-mating factor receptor with rluorescent ligands

Three analogues of the alpha-mating factor pheromone of Saccharomyces cerevisiae containing the 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) group were synthesized that had high binding affinity to the receptor and retained biological activity. The fluorescence emission maximum of the NBD group in [K7(NBD),Nle(12)]-alpha-factor was blue shifted by 35 nm compared to buffer when the pheromone bound to its receptor. Fluorescence quenching experiments revealed that the NBD group in [K7(NBD),Nle(12)]-alpha-factor bound to the receptor was shielded from collision with iodide anion when in aqueous buffer. In contrast, the emission maximum of NBD in [K7(ahNBD),Nle(12)]-alpha-factor or [Orn7(NBD),Nle(12)]-alpha-factor was not significantly shifted and iodide anion efficiently quenched the fluorescence of these derivatives when they were bound to receptor. The fluorescence investigation suggests that when the alpha-factor is bound to its receptor, K7 resides in an environment that has both hydrophobic and hydrophilic groups within a few angstroms of each other.

Multiplicity and regulation of genes encoding peptide transporters in Saccharomyces cerevisiae

The model eukaryote Saccharomyces cerevisiae has two distinct peptide transport mechanisms, one for di-/tripeptides (the PTR system) and another for tetra-/pentapeptides (the OPT system). The PTR system consists of three genes, PTR1, PTR2 and PTR3. The transporter (Ptr2p), encoded by the gene PTR2, is a 12 transmembrane domain (TMD) integral membrane protein that translocates di-/tripeptides. Homologues to Ptr2p have been identified in virtually all organisms examined to date and comprise the PTR family of transport proteins. In S. cerevisiae, the expression of PTR2 is highly regulated at the cellular level by complex interactions of many genes, including PTR1, PTR3, CUP9 and SSY1. Oligopeptides, consisting of four to five amino acids, are transported by the 12-14 TMD integral membrane protein Opt1p. Unlike Ptr2p, distribution of this protein appears limited to fungi and plants, and there appears to be three paralogues in S. cerevisiae. This transporter has an affinity for enkephalin, an endogenous mammalian pentapeptide, as well as for glutathione. Although it is known that OPT1 is normally expressed only during sporulation, to date little is known about the genes and proteins involved in the regulation of OPT1 expression.

Synthesis and biophysical analysis of transmembrane domains of a Saccharomyces cerevisiae G protein-coupled receptor

The Ste2p receptor for alpha-factor, a tridecapeptide mating pheromone of the yeast Saccharomyces cerevisiae, belongs to the G protein-coupled family of receptors. In this paper we report on the synthesis of peptides corresponding to five of the seven transmembrane domains (M1-M5) and two homologues of the sixth transmembrane domain corresponding to the wild-type sequence and a mutant sequence found in a constitutively active receptor. The secondary structures of all new transmembrane peptides and previously synthesized peptides corresponding to domains 6 and 7 were assessed using a detailed CD analysis in trifluoroethanol, trifluoroethanol-water mixtures, sodium dodecyl sulfate micelles, and dimyristoyl phosphatidyl choline bilayers. Tryptophan fluorescence quenching experiments were used to assess the penetration of the membrane peptides into lipid bilayers. All peptides were predominantly (40-80%) helical in trifluoroethanol and most trifluoroethanol-water mixtures. In contrast, two of the peptides M3-35 (KKKNIIQVLLVASIETSLVFQIKVIFTGDNFKKKG) and M6-31 (KQFDSFHILLINleSAQSLLVPSIIFILAYSLK) formed stable beta-sheet structures in both sodium dodecyl sulfate micelles and DMPC bilayers. Polyacrylamide gel electrophoresis showed that these two peptides formed high molecular aggregates in the presence of SDS whereas all other peptides moved as monomeric species. The peptide (KKKFDSFHILLIMSAQSLLVLSIIFILAYSLKKKS) corresponding to the sequence in the constitutive mutant was predominantly helical under a variety of conditions, whereas the homologous wild-type sequence (KKKFDSFHILLIMSAQSLLVPSIIFILAYSLKKKS) retained a tendency to form beta-structures. These results demonstrate a connection between a conformational shift in secondary structure, as detected by biophysical techniques, and receptor function. The aggregation of particular transmembrane domains may also reflect a tendency for intermolecular interactions that occur in the membrane environment facilitating formation of receptor dimers or multimers.

Synthesis and biological evaluation of the geometric farnesylated analogues of the a-factor mating peptide of Saccharomyces cerevisiae

The a-factor of Saccharomyces cerevisiae is a dodecapeptide pheromone (YIIKGVFWDPAC(Farnesyl)-OCH(3), 1), in which post-translational modification with a farnesyl isoprenoid and carboxymethyl group is required for full biological activity. This peptide has been used as a model system to explore the biological function of the farnesylcysteine moiety, which is found on and required for the biological activity of many key mammalian proteins. The objective of this particular study was the determination of the biological effect of double bond isomerization of the natural E, E-farnesyl moiety on the biological activity of the a-factor. A unified, stereoselective synthetic route to the three geometric isomers of E,E-farnesol (12, 13, and 14) has been developed. The key feature of this synthesis is the ability to control the stereochemistry of triflation of the beta-ketoester 22 to give either 23 or 25. The three farnesol isomers were converted to the corresponding isomeric a-factors (9, 10 and 11) via a modified version of a previously utilized synthetic route. Biological evaluation of these peptides indicates that, surprisingly, all three possess nearly equivalent activity to the natural a-factor bearing the E,E-farnesyl moiety.

Fatal and near-fatal asthma in children exposed to fireworks

BACKGROUND

Fireworks accounted for an estimated 8,300 emergency department visits during 1997 in the United States. Firecrackers, bottle rockets, roman candles, and sparklers contribute to the most hospitalizations. Burns account for the majority of these injuries Fireworks are manufactured from a variety of chemicals, which include the known irritant, sulfur dioxide, as one of the products of combustion. We are reporting one fatal and one near fatal asthma exacerbation after use of fireworks.

OBJECTIVE

We are reporting two patients who had severe asthma exacerbation shortly after having exposure to different types of fireworks.

METHODS

Patient data were collected from patients that presented the week of July 4, 1998 to our institution. Information was also obtained from the Consumer Product Safety Commission and the National Weather Service.

RESULT

The patients presented to our institution within hours of their exposure from the fireworks. One patient had a respiratory arrest and was resuscitated, but subsequently expire. The second patient was able to treated aggressively and avoided intubation.

CONCLUSIONS

These cases demonstrate risks that fireworks may present to the asthmatic child and that patient's with asthma should exercise caution when observing or participating in fireworks demonstrations.

NK-1 antagonist reduces colonic inflammation and oxidative stress in dextran sulfate-induced colitis in rats

Although substance P (SP) has been implicated as a mediator of neurogenic inflammation in the small intestine, little information is available regarding the role of SP in the pathogenesis of chronic ulcerative colitis. In this study, our aim was to investigate whether the intraperitoneal administration of a nonpeptide neurokinin-1 (NK-1) antagonist, CP-96345, which antagonizes the binding of SP to its NK-1 receptor, results in the attenuation of colonic inflammation induced in rats by 5% dextran sodium sulfate (DSS) in drinking water for 10 days compared with an inactive enantiomer, CP-96344. Disease activity was assessed daily for 10 days, after which colonic tissue damage was scored and myeloperoxidase activity and colon and urinary 8-isoprostanes were measured. Animals receiving DSS exhibited marked physical signs of colitis by day 5 compared with controls. Chronic administration of the NK-1 antagonist significantly reduced the disease activity index, mucosal myeloperoxidase activity, colonic tissue damage score, and mucosal and urinary levels of 8-isoprostanes compared with inactive enantiomer- or vehicle-injected (saline) animals receiving DSS alone. These data indicate that the administration of an NK-1 antagonist can attenuate colonic inflammation and oxidative stress and suggest a novel therapeutic approach in the treatment of chronic ulcerative colitis.

Position 13 analogs of the tridecapeptide mating pheromone from Saccharomyces cerevisiae: design of an iodinatable ligand for receptor binding

Analogs of the alpha-factor tridecapeptide mating pheromone (WHWLQLKPGQPMY) from Saccharomyces cerevisiae in which Tyr13 was replaced with Phe, p-F-Phe, m-F-Phe, p-NO2-Phe, p-NH2-Phe or Ser were synthesized and purified to >99% homogeneity. These analogs were bioassayed using a growth arrest assay and a gene induction assay and evaluated for their ability to compete with binding of tritiated alpha-factor to its receptor Ste2p. The results showed that the phenolic OH of Tyr13 is not required for either biological activity or receptor recognition. Analogs containing fluorine, amino, nitro or a hydrogen in place of OH had 80-120% of the biological activity of the parent pheromone in the gene induction assay and had receptor affinities from nearly equal to 6-fold lower than that of alpha-factor. In contrast, substitution of Ser or Ala at position 13 resulted in a >100-fold decrease in receptor affinity suggesting that the aromatic ring is involved in binding to the receptor. The lack of a strict requirement for Tyr13 allowed the design of several multiple replacement analogs in which Phe or p-F-Phe were substituted at position 13 and Tyr was placed in other positions of the peptide. These analogs could then be iodinated and used in the development of a highly sensitive receptor-binding assay. One potential receptor ligand [Tyr(125I)1,Nle12, Phe13] alpha-factor exhibited saturable binding with a KD of 81 nM and was competed by alpha-factor for binding in a whole-cell assay. Thus a new family of radioactive ligands for the alpha-factor receptor has been revealed. These ligands should be extremely useful in defining active site residues during mutagenesis and cross-linking studies.

Conformational analysis of cyclic analogues of the Saccharomyces cerevisiae alpha-factor pheromone

Analogues of the alpha-factor mating pheromone (WHWLQLKPGQPMY) from Saccharomyces cerevisiae in which the side chains of residues 7 and 10 were joined by lactam bonds were studied by nmr and molecular modeling. These investigations were carried out to discern the effect of lactam ring size on conformation and to ascertain whether the side chain i to i + 3 cyclized tetramers [H. R. Marepalli et al. (1996) Journal of the American Chemical Society, Vol. 118, pp. 6531-6539] can be considered as conformation-constraining building blocks when introduced into a long peptide chain. Nuclear Overhauser effect constraints, temperature coefficients, and backbone torsional angles were derived from 1H-nmr spectra measured in DMSO-d6. Modeling studies using the above constraints indicate that the lactam regions of the tridecapeptides assume various combinations of type II beta-turns, gamma-turns, and gamma 1-turns, but never type I beta-turns. These investigations provide evidence that the tetrapeptide building blocks retain their preferred conformations in larger molecules and can be used to control the architecture of regions of such peptides.

Synthesis of prenylated peptides and peptide esters

Modification of the cysteine sulfur in peptides and proteins to a thioether is a recently described posttranslational event that results in the incorporation of farnesyl and geranylgeranyl moieties. The increased lipophilicity accompanying these modifications often causes localization of the resulting protein to the membrane and may be essential for biological activity. Methods are described to chemically and biochemically synthesize farnesylated and geranylgeranylated peptides and proteins from microgram to gram quantities. Conditions for thioalkylation include acidic, neutral, and basic media. The ability to readily form peptidylthioethers will greatly facilitate studies of biologically important proteins and peptides containing isoprenyl moieties.

A limited spectrum of mutations causes constitutive activation of the yeast alpha-factor receptor

Activation of G protein coupled receptors (GPCRs) by binding of ligand is the initial event in diverse cellular signaling pathways. To examine the frequency and diversity of mutations that cause constitutive activation of one particular GPCR, the yeast alpha-factor receptor, we screened libraries of random mutations for constitutive alleles. In initial screens for mutant receptor alleles that exhibit signaling in the absence of added ligand, 14 different point mutations were isolated. All of these 14 mutants could be further activated by alpha-factor. Ten of the mutants also acquired the ability to signal in response to binding of desTrp(1)¿Ala(3)ălpha-factor, a peptide that acts as an antagonist toward normal alpha-factor receptors. Of these 10 mutants, at least eight alleles residing in the third, fifth, sixth, and seventh transmembrane segments exhibit bona fide constitutive signaling. The remaining alleles are hypersensitive to alpha-factor rather than constitutive. They can be activated by low concentrations of endogenous alpha-factor present in MATa cells. The strongest constitutively active receptor alleles were recovered multiple times from the mutational libraries, and extensive mutagenesis of certain regions of the alpha-factor receptor did not lead to recovery of any additional constitutive alleles. Thus, only a limited number of mutations is capable of causing constitutive activation of this receptor. Constitutive and hypersensitive signaling by the mutant receptors is partially suppressed by coexpression of normal receptors, consistent with preferential association of the G protein with unactivated receptors.

Role of a hyaluronate-based membrane in the prevention of peritonitis-induced adhesions

Adhesions remain a significant postoperative complication of abdominal surgery; however, recent evidence suggests that physical barriers may reduce their incidence. Although these adhesion prevention barriers are efficacious when used under aseptic conditions, little is known about their use in the presence of peritonitis, which is associated with an increased incidence of abdominal adhesions. A sodium hyaluronate and carboxymethylcellulose bioresorbable membrane (HA membrane) has been shown recently to reduce postoperative adhesions in several animal models and in two clinical trials. To investigate the efficacy of HA membrane in the presence of peritonitis, generalized peritonitis was induced in rats by either cecal ligation and puncture (CLP) or cecal ligation (CL) alone. The ceca were resected after 12 hours, and animals were randomly assigned to receive or not receive HA membrane applied to the cecum. At day 7, abdominal adhesions and abscesses were scored. In the presence of peritonitis, HA membrane did not significantly reduce the number or tenacity of adhesions. A trend toward increased abscess formation was associated with HA membrane in the CL group. Although HA membrane has been shown to reduce the incidence and severity of abdominal adhesions under aseptic conditions, this study demonstrates that it is not efficacious in preventing abdominal adhesions in the presence of peritonitis. The association between HA membrane and abscess formation in the presence of experimental peritonitis requires further investigation.

Role of transforming growth factor beta-1 in peritonitis-induced adhesions

Peritonitis is a major cause of intra-abdominal adhesion formation. The overexpression of transforming growth factor beta-1 (TGF-Beta1), a potent mitogen, chemoattractant, and stimulant for collagen synthesis by fibroblasts, has been linked to tissue fibrosis at various sites throughout the body including peritoneal adhesion formation. Hence we hypothesized that the mechanism(s) involved in peritonitis-induced adhesion formation may be mediated through the upregulation of TGF-Beta1 expression. Peritonitis was induced in rats by cecal ligation and puncture, while a control group underwent sham operation. Adhesions were scored and harvested from both groups at 0, 6 and 12 hours and at 1, 2, 4, 7, and 28 days. Tissue expression of TGF-Beta1 mRNA was determined by quantitative reverse transcription-polymerase chain reaction and TGF-Beta1 protein was localized by immunohistochemical analysis. Serum and peritoneal fluid TGF-Beta1 concentrations were quantified by enzyme-linked immunosorbent assay. Compared with sham operation, peritonitis was associated with a significantly greater incidence of abdominal adhesions and a significant increase in the levels of TGF-Beta1 mRNA expression at days 2, 4, and 7. Immunostaining intensity of TGF-Beta1 in adhesions from the peritonitis group also steadily rose through day 7. In peritoneal fluid, the ratio of active:total TGF-Beta1 was significantly increased in the peritonitis group on days 1, 2, and 4 compared with the sham group. These results suggest that peritonitis is associated with the upregulation of TGF-Beta1, a mechanism that may exacerbate adhesion formation.

Role of stasis and oxidative stress in ileal pouch inflammation

BACKGROUND

Although ileal pouch-anal anastomosis has become the operation of choice for patients with chronic ulcerative colitis and familial adenomatous polyposis coli, ileal pouch inflammation or pouchitis remains a significant postoperative complication. Numerous factors such as fecal stasis have been implicated in the etiology of pouchitis; however, pouchitis remains poorly understood due to the lack of a small animal model. One of the primary goals of this study was to surgically create a reservoir or U-pouch in the ileum of a rat in which stasis would occur in a manner that was unimpeded by other complicating factors such as a colectomy. This model would allow investigation of the hypothesis that intestinal stasis leads to biochemical changes that predispose the ileal pouch to inflammation and oxidative stress.

MATERIALS AND METHODS

A U-pouch was surgically created in the terminal ileum of Lewis rats just proximal to the ileocecal valve without a colectomy. Stasis was assessed by serial barium radiographs over 48 h. Thirty days after surgery, mucosa was obtained from the ileal U-pouches and nonoperated ileum to assess inflammation and neutrophil infiltration histologically and by measuring myeloperoxidase activity. Oxidative stress was assessed by measuring 8-isoprostane levels in urine. Once the model was validated and it was established that stasis and inflammation occurred in the pouch, either vitamin E or allopurinol was administered for 30 days after which myeloperoxidase and 8-isoprostane levels were again measured.

RESULTS

In our experimental model, ileal stasis resulted in increases in both mucosal myeloperoxidase activity and urinary 8-isoprostane levels, suggesting that oxidative stress was associated with stasis. Thirty-day treatment with vitamin E or allopurinol reduced ileal myeloperoxidase activity and urinary 8-isoprostane levels.

CONCLUSION

These studies demonstrated that stasis in the ileum occurred and was associated with neutrophil infiltration and oxidative stress. Antioxidant treatment reduced the inflammatory response suggesting a role for antioxidant therapy in the treatment of pouchitis.

Structure, biological activity and membrane partitioning of analogs of the isoprenylated a-factor mating peptide of Saccharomyces cerevisiae

Previous biochemical investigations on the Saccharomyces cerevisiae a-factor indicated that this lipopeptide pheromone [YIIKGVFWDPAC(farnesyl)OMe] might adopt a type II beta-turn at positions 4 and 5 of the peptide sequence. To test this hypothesis, we synthesized five analogs of a-factor, in which residues at positions 4 and 5 were replaced with: L-Pro4(I); D-Pro4(II); L-Pro4-D-Ala5(III); D-Pro4-L-Ala5(IV); or Nle4(V). Analogs were purified to > 99% homogeneity as evidenced by HPLC and TLC and were characterized by mass spectrometry and amino acid analysis. Using a growth arrest assay the conformationally restricted a-factor analogs I and III were found to be almost 50-fold more active than the diastereometric homologs II and IV and were equally active to wild-type a-factor. Replacement of Lys4 with the isosteric Nle4 almost abolished the activity of the pheromone. Thus, the incorporation of residues that promote a type II beta-turn compensated for the loss of the favorable contribution of the Lys4 side chain to pheromone activity. CD spectra on these peptides suggested that they were essentially disordered in both TFE/H2O and in the presence of DMPC vesicles. There was no correlation between CD peak shape and biological activity. Using fluorescence spectroscopy we measured the interaction of lipid vesicles with these position 4 and 5 analogs as well as with three a-factor analogs with a modified farnesyl group. The results indicated that modifications of both the peptide sequence and the lipid moiety affect partitioning into lipid, and that no correlation existed between the propensity of a pheromone to partition into the lipid and its biological activity.

Enkephalins are transported by a novel eukaryotic peptide uptake system

We have identified an oligopeptide transporter in the yeast Saccharomyces cerevisiae which mediates the uptake of tetra- and pentapeptides, including the endogenous opioids leucine enkephalin (Tyr-Gly-Gly-Phe-Leu) and methionine enkephalin (Tyr-Gly-Gly-Phe-Met). The transporter is encoded by the gene OPT1. Yeast expressing OPT1 can utilize enkephalins to satisfy amino acid auxotrophic requirements for growth. The transport of radiolabeled leucine enkephalin exhibits saturable kinetics, with a K(m) of 310 microM. Transport activity is optimum at acidic pH and sensitive to reagents which uncouple oxidative phosphorylation, suggesting an energy dependence on the proton gradient. Growth, transport, and chromatographic data indicate that leucine enkephalin is not hydrolyzed in the extracellular medium and as such is translocated intact across the cell membrane. The system is specific for tetra- and pentapeptides and can be inhibited by the opioid receptor antagonists naloxone and naltrexone. To date, this is the first example of a eukaryotic transport system which can use enkephalins as a substrate, opening the possibility that a homologue exists in higher eukaryotes.

WdChs4p, a homolog of chitin synthase 3 in Saccharomyces cerevisiae, alone cannot support growth of Wangiella (Exophiala) dermatitidis at the temperature of infection

By using improved transformation methods for Wangiella dermatitidis, and a cloned fragment of its chitin synthase 4 structural gene (WdCHS4) as a marking sequence, the full-length gene was rescued from the genome of this human pathogenic fungus. The encoded chitin synthase product (WdChs4p) showed high homology with Chs3p of Saccharomyces cerevisiae and other class IV chitin synthases, and Northern blotting showed that WdCHS4 was expressed at constitutive levels under all conditions tested. Reduced chitin content, abnormal yeast clumpiness and budding kinetics, and increased melanin secretion resulted from the disruption of WdCHS4 suggesting that WdChs4p influences cell wall structure, cellular reproduction, and melanin deposition, respectively. However, no significant loss of virulence was detected when the wdchs4Delta strain was tested in an acute mouse model. Using a wdchs1Delta wdchs2Delta wdchs3Delta triple mutant of W. dermatitidis, which grew poorly but adequately at 25 degrees C, we assayed WdChs4p activity in the absence of activities contributed by its three other WdChs proteins. Maximal activity required trypsin activation, suggesting a zymogenic nature. The activity also had a pH optimum of 7.5, was most stimulated by Mg(2+), and was more inhibited by polyoxin D than by nikkomycin Z. Although the WdChs4p activity had a broad temperature optimum between 30 to 45 degrees C in vitro, this activity alone did not support the growth of the wdchs1Delta wdchs2Delta wdchs3Delta triple mutant at 37 degrees C, a temperature commensurate with infection.

Ileal pouch salvage following failed ileal pouch- anal anastomosis

Attempts have been made to salvage failed ileal pouch-anal anastomoses (IPAA) performed for ulcerative colitis or familial polyposis coli. These can be categorized as total reconstruction of the IPAA, partial transabdominal approach, and partial transperineal approach. The aims of our study were to determine the overall success of pouch salvage; to examine the demographics, indications, and outcomes for each approach; and to assess anorectal physiology and patient satisfaction in those with successful salvage operations. We reviewed data, including results of anorectal manometry, from 29 patients undergoing salvage procedures for failed IPAA. Seventeen salvage attempts were successful, 11 attempts failed, and one patient was lost to follow-up. Success rates were 100% in the total reconstruction group, 25% in the partial transabdominal group, and 55% in the transperineal group. In those undergoing total reconstruction of the IPAA (n = 9), functional outcome, as measured by incontinence, improved with 50% reporting incontinence preoperatively compared to 0% postoperatively (P = 0.055). Mean 24-hour stool frequency and nighttime stool frequency declined. All patients reported satisfaction with their outcomes. Sixty percent of patients who underwent ileal pouch salvage following IPAA have been successful in avoiding permanent ileostomy. These results suggest that a continued effort to salvage failed IPAA, including the use of total reconstruction, is a viable alternative to permanent ileostomy.

Long-distance rotational echo double resonance measurements for the determination of secondary structure and conformational heterogeneity in peptides

The utility of rotational echo double resonance (REDOR) NMR spectroscopy for determining the conformations of linear peptides has been examined critically using a series of crystalline and amorphous samples. The focus of the present work was the evaluation of long-distance (> 5 A) interactions using 13C-15N dephasing. Detailed studies of specifically labeled melanostatin and synthetic analogs of the alpha-factor yeast mating hormone show that nitrogen-dephased, carbon-observe REDOR measurements are reliable for distances up to 6.0 A, and that dipolar interactions can be detected for distances up to 7 A. By contrast, nitrogen-observe REDOR gives reliable results only for distances shorter than 5.0 A. To measure distances accurately, REDOR data must be corrected for the effects of natural-abundance spins. These corrections are particularly important for measuring long distances, which are of the greatest value for determining peptide secondary structure. We have developed a spherical shell model for calculating the effect of these background spins. The REDOR studies also indicate that in a lyophilized powder, the tridecapeptide alpha-factor mating pheromone from Saccharomyces cerevisiae (WHWLQLKPGQPMY) probably exists as a distribution of different turn structures around the KPGQ region. This finding revises previous solid-state NMR studies on this peptide, which concluded alpha-factor assumes a distorted type-I beta-turn in the Pro-Gly central region of the molecule [J.R. Garbow, M. Breslav, O. Antohi, F. Naider, Biochemistry, 33 (1994) 10094].

Surgical therapy for ulcerative colitis and Crohn's disease

Over the past 2 decades there has been considerable progress in the surgical management of inflammatory bowel disease. Crohn's disease is a chronic, nonspecific inflammatory disease of the gastrointestinal tract of unknown cause. It involves mainly the ileum, colon, and rectum, most often producing symptoms of obstruction or localized perforation with fistula. Although surgical treatment is palliative, operative excision in combination with strictureplasty, where appropriate, provides effective symptomatic relief and reasonable long-term benefit. Chronic ulcerative colitis is a diffuse inflammatory disease of the mucosal lining of the colon and rectum. Total removal of the colon and rectum provides a complete cure. Newer surgical alternatives, developed over the last 2 decades, have eliminated the need for a permanent ileostomy following definitive resection of the involved colon and rectum.

Oral versus intravenous corticosteroids in children hospitalized with asthma

BACKGROUND

Previous studies have demonstrated that in the emergency treatment of an asthma exacerbation, corticosteroids used in conjunction with beta-agonists result in lower hospitalization rates for children and adults. Furthermore, orally administered corticosteroids have been found to be effective in the treatment of outpatients with asthma. However, similar data in inpatients is lacking.

OBJECTIVE

The purpose of this study was to determine the efficacy of oral prednisone versus intravenous methylprednisolone in equivalent doses for the treatment of an acute asthma exacerbation in hospitalized children.

METHODS

We conducted a randomized, double-blind, double-placebo study comparing oral prednisone at 2 mg/kg/dose (maximum 120 mg/dose) twice daily versus intravenous methylprednisolone at 1 mg/kg/dose (maximum 60 mg/dose) four times daily in a group of patients 2 through 18 years of age hospitalized for an acute asthma exacerbation. All patients were assessed by a clinical asthma score 3 times a day. The main study outcome was length of hospitalization; total length of stay and time elapsed before beta-agonists could be administered at 6-hour intervals. Duration of supplemental oxygen administration and peak flow measurements were secondary outcome measures.

RESULTS

Sixty-six patients were evaluated. Children in the prednisone group had a mean length of stay of 70 hours compared with 78 hours for the methylprednisolone group (P =.52). Children in the prednisone group were successfully weaned to beta-agonists in 6-hour intervals after 59 hours compared with 68 hours for the methylprednisolone group (P =.47). Patients receiving prednisone required supplemental oxygen for 30 hours compared with 52 hours for the methylprednisolone group (P =.04).

CONCLUSION

There was no difference in length of hospital stay between asthmatic patients receiving oral prednisone and those receiving intravenous methylprednisolone. Because hospitalization charges are approximately 10 times greater for intravenous methylprednisolone compared with oral prednisone, the use of oral prednisone to treat inpatients with acute asthma would result in substantial savings.

Mutations affecting ligand specificity of the G-protein-coupled receptor for the Saccharomyces cerevisiae tridecapeptide pheromone

Random mutations were generated in the G-protein-coupled receptor (Ste2p) for the tridecapeptide pheromone (alpha-factor) of Saccharomyces cerevisiae. These mutants were screened for variants that responded to antagonists. Because multiple mutations were detected in each mutant receptor recovered from the screen, site-directed mutagenesis was used to create single-site mutant receptors. Three receptors containing mutations F55V, S219P, and S259P were analyzed for their biological responses to various alpha-factor analogs and for their ligand binding profiles. Cells expressing each of the mutant receptors responded to alpha-factor as well as or better than wild-type cells in a growth arrest assay. In contrast, the binding of alpha-factor to the F55V and S219P mutant receptors was at least 10-fold reduced in comparison to wild-type receptor indicating a complex non-linear correlation between binding affinity and biological activity. Cells expressing mutant receptors responded to some normally inactive analogs in biological assays, despite the fact that these analogs had a low affinity for Ste2p. The analysis of these mutant receptors confirms previous findings that the first and sixth transmembrane regions of Ste2p are important for ligand interaction, ligand specificity, and/or receptor activation to initiate the signal transduction pathway. Changes in binding affinity of pheromone analogs to wild-type and mutant receptors indicate that residue 55 of Ste2p is involved with both ligand binding and signal transduction.

Altered expression of selectable marker URA3 in gene-disrupted Candida albicans strains complicates interpretation of virulence studies

The ura-blaster technique for the disruption of Candida albicans genes has been employed in a number of studies to identify possible genes encoding virulence factors of this fungal pathogen. In this study, the URA3-encoded orotidine 5'-monophosphate (OMP) decarboxylase enzyme activities of C. albicans strains with ura-blaster-mediated genetic disruptions were measured. All strains harboring genetic lesions via the ura-blaster construct showed reduced OMP decarboxylase activities compared to that of the wild type when assayed. The activity levels in different gene disruptions varied, suggesting a positional effect on the level of gene expression. Because the URA3 gene of C. albicans has previously been identified as a virulence factor for this microorganism, our results suggest that decreased virulence observed in strains constructed with the ura-blaster cassette cannot accurately be attributed, in all cases, to the targeted genetic disruption. Although revised methods for validating a URA3-disrupted gene as a target for antifungal drug development could be devised, it is clearly desirable to replace URA3 with a different selectable marker that does not influence virulence.

Structure of segments of a G protein-coupled receptor: CD and NMR analysis of the Saccharomyces cerevisiae tridecapeptide pheromone receptor

Peptides representing both loop and the sixth transmembrane regions of the alpha-factor receptor of Saccharomyces cerevisiae were synthesized by solid-phase procedures and purified to near homogeneity. CD, nmr, and modeling analysis indicated that in aqueous media the first extracellular loop peptide E1(107-125), the third intracellular loop peptide I3(231-243), and the carboxyl terminus peptide I4(350-372) were mostly disordered. In contrast, the second extracellular loop peptide E2(191-206) assumed a well-defined structure in aqueous medium and the sixth transmembrane domain peptide receptor M6(252-269, C252A) was highly helical in trifluoroethanol/water (4:1), exhibiting a kink at Pro258. A synthetic peptide containing a sequence similar to that of the sixth transmembrane domain of a constitutively active alpha-factor receptor M6(252-269, C252A, P258L) in which Leu replaces Pro258 exhibited significantly different biophysical properties than the wild-type sequence. In particular, this peptide had very low solubility and gave CD resembling that of a beta-sheet structure in hexafluoroacetone/water (1:1) whereas the wild-type peptide was partially helical under identical conditions. These results would be consistent with the hypothesis that the constitutive activity of the mutant receptor is linked to a conformational change in the sixth transmembrane domain. The study of the receptor segments also indicate that peptides corresponding to loops of the alpha-factor receptor do not appear to assume turn structures.

Synthesis, biological activity, and conformational analysis of peptidomimetic analogues of the Saccharomyces cerevisiae alpha-factor tridecapeptide

Biochemical and biophysical investigations on the Saccharomyces cerevisiae alpha-factor indicate that this tridecapeptide mating pheromone (WHWLQLKPGQPMY) might adopt a type II beta-turn in the center of the peptide when it binds to its G protein-coupled receptor. To test this hypothesis we synthesized analogues of alpha-factor incorporating a (R or S)-gamma-lactam conformational constraint [3-(R or S)-amino-2-oxo-1-pyrrolidineacetamido] in place of the Pro-Gly at residues 8 and 9 of the peptide and tested their biological activities and receptor binding. Analogues were purified to >99% homogeneity as evidenced by high-performance liquid chromatography and capillary electrophoresis and characterized by amino acid analysis, mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. The restricted alpha-factor analogue WHWLQLK[(R)-gamma-lactam]QP[Nle]Y was more active than its lactam-containing diastereomeric homologue WHWLQLK[(S)-gamma-lactam]QP[Nle]Y and about equally active with the [Nle12]-alpha-factor in growth arrest and FUS1-lacZ gene induction assays. Both lactam analogues competed with tritiated [Nle12]-alpha-factor for binding to the alpha-factor receptor (Ste2p) with the (R)-gamma-lactam-containing peptide having 7-fold higher affinity than the (S)-gamma-lactam-containing homologue. Two-dimensional NMR spectroscopy and modeling analysis gave evidence that the (R)-gamma-analogue is a flexible peptide that assumes a transient gamma-turn structure around the lactam moiety. The results represent the first example of an alpha-factor analogue containing a peptidomimetic constraint that is as active as the native pheromone. The correlation between activity and structure provides further evidence that the biologically active conformation of the molecule contains a turn in the middle of the pheromone. This study provides new insights into the structural basis of alpha-factor activity and adds to the repertoire of conformationally biasing constraints that can be used to maintain and even enhance biological activity in peptide hormones.

Structure-function analysis of the Saccharomyces cerevisiae tridecapeptide pheromone using alanine-scanned analogs

Twenty-six peptide analogs of the Saccharomyces cerevisiae alpha-factor, a tridecapeptide mating pheromone (W1H2W3L4Q5L6K7p8G9Ql0P11M12Y13) with either L- or D-alanine replacement of each amino acid residue (Ala-scanned) and with the isosteric replacement of methionine at position 12 by norleucine, were synthesized, purified to homogeneity and assayed for biological activity and receptor binding. Two new and effective antagonists, [D-Ala3,Nle12]alpha-factor and [D-Ala4,Nle12]alpha-factor, were found among the series, and the [D-Ala10,Nle12]alpha-factor demonstrated a marked ability to increase the biological activity of [Nle12]alpha-factor without having any effect by itself. One analog, the [L-Ala1 alpha-factor, showed a 3-fold increase in bioactivity over the [Nle12]alpha-factor, although its binding to the alpha-factor receptor was about 70-fold less than [Nle12]alpha-factor. Residues near the carboxyl terminus contributed more strongly to receptor binding than other residues, whereas those near the amine terminus of the alpha-factor played an important role in signal transduction. The effect of insertion of D-Ala residues at positions 7, 8, 9 and 10 on bioactivity and receptor binding of the peptide suggested a specific positioning role of the central loop in establishing optimal contacts between the receptor and the ends of the pheromone. We conclude that the alpha-factor may be divided into segments with dominant roles in forming the biologically active pheromone conformation, in receptor binding and in initiating signal transduction. The discovery of such relationships was made possible by the systematic variation of each residue in the peptide and by the testing of each analog in highly defined biological and binding assays.

PTR3, a novel gene mediating amino acid-inducible regulation of peptide transport in Saccharomyces cerevisiae

We have isolated and characterized the Saccharomyces cerevisiae PTR3 gene by functional complementation of a mutant deficient for amino acid-inducible peptide transport. PTR3 is predicted to encode a protein of 678 amino acids that exhibits no similarity to any other protein in the database. Deletion of the PTR3 open reading frame pleiotropically reduced the sensitivity to toxic peptides and amino acid analogues. Initial rates of radiolabelled dipeptide uptake demonstrated that elimination of PTR3 resulted in the loss of amino acid-induced levels of peptide transport. PTR3 was required for amino acid-induced expression of PTR2, the gene encoding the dipeptide/tripeptide transport protein, but was not necessary for nitrogen catabolite repression of peptide import or PTR2 expression. It was determined that PTR3 also modulates expression of BAP2, the gene encoding the branched-amino acid permease. Furthermore, we present genetic evidence that suggests that PTR3 functions within a novel regulatory pathway that facilitates amino acid induction of the PTR system.

Eighteen years' experience with neonatal Hirschsprung's disease treated by endorectal pull-through without colostomy

METHODS

In the past 18 years, the authors have treated 84 patients with Hirschsprung's disease. Of these, 43 patients were under 1 month of age and underwent endorectal pull-through without colostomy. Some have undergone follow-up for as long as 18 years.

RESULTS

Thirty-four of these 43 (79%) newborn patients were available for follow-up. Twenty-two were totally continent. The remaining 12 have normal sphincter tone. Of the 41 patients above 1 month of age, 34 (83%) were available for follow-up. Some have undergone follow-up for as long as 18 years.

CONCLUSION

Twenty-two of this latter group (79%) have normal bowel control.

Schizosaccharomyces pombe isp4 encodes a transporter representing a novel family of oligopeptide transporters

We have recently cloned an oligopeptide transport gene from Candida albicans denoted OPT1. This gene showed significant sequence similarity to three open reading frames (ORFs) with no previously established function: isp4 from Schizosaccharomyces pombe and Saccharomyces cerevisiae YJL212C and YPR194C, identified during the genome project. The S. pombe gene isp4 was originally identified by Sato et al. as a gene that was upregulated through nitrogen starvation induction of meiosis. However, an isp4delta strain exhibited a wild-type phenotype with respect to sexual differentiation. We have found that the same isp4delta strain is deficient in tetrapeptide transport activity as measured by its resistance to toxic tetrapeptides, by its inability to accumulate a radiolabelled tetrapeptide and by the inability to use tetrapeptides as a sole source of an amino acid to satisfy an auxotrophic requirement. Similarly, we found that the ORF YPR194C from S. cerevisiae encodes an oligopeptide transporter. Sequence analyses as well as physiological evidence has led us to propose that the proteins encoded by isp4 and the genes identified from S. cerevisiae and C. albicans comprise a new group of transporters specific for small oligopeptides, which we have named the OPT family.

Linkage of adhesion, filamentous growth, and virulence in Candida albicans to a single gene, INT1

Adhesion and the ability to form filaments are thought to contribute to the pathogenicity of Candida albicans, the leading cause of fungal disease in immunocompromised patients. Int1p is a C. albicans surface protein with limited similarity to vertebrate integrins. INT1 expression in Saccharomyces cerevisiae was sufficient to direct the adhesion of this normally nonadherent yeast to human epithelial cells. Furthermore, disruption of INT1 in C. albicans suppressed hyphal growth, adhesion to epithelial cells, and virulence in mice. Thus, INT1 links adhesion, filamentous growth, and pathogenicity in C. albicans and Int1p may be an attractive target for the development of antifungal therapies.

Effects of hyaluronic acid/carboxymethylcellulose gel on bowel anastomoses in the New Zealand white rabbit

Intra-abdominal adhesions form in more than 90% of patients undergoing major abdominal surgery and can lead to significant complications. Application of a bioresorbable gel consisting of chemically modified hyaluronic acid (HA) and carboxymethylcellulose (CMC) has shown promise as a means of preventing intra-abdominal adhesions, but there have been concerns that the presence of the gel might interfere with the integrity and healing of bowel anastomoses. We tested the effects of HA/CMC gel on adhesion formation and anastomotic healing in 60 New Zealand white rabbits after transection and complete (100%) or incomplete (90%) anastomosis of the ileum. Half of the animals underwent application of HA/CMC gel and half served as control subjects. Animals were killed at 4, 7, or 14 days after surgery. Anastomotic adhesions were scored in a blinded fashion. Integrity of the anastomosis was tested by measuring bursting pressure at the anastomotic site and in an adjacent section of intact bowel. With complete anastomosis, HA/CMC gel significantly reduced adhesion formation at 7 and 14 days after surgery (P<0.05), but gel application did not inhibit adhesion formation when the anastomosis was incomplete. Anastomosed segments of bowel burst at a lower pressure than intact bowel 4 days after surgery, but bursting pressures were normal at 7 and 14 days. Burst pressures of anastomoses receiving an application of HA/CMC gel were nearly identical to control anastomoses at all three time points. HA/CMC gel did not interfere with the normal healing process of bowel anastomoses. Furthermore, HA/CMC gel decreased adhesion formation after complete anastomoses, yet it did not affect adhesion formation in the presence of anastomotic disruption.