Transection of Gustatory Nerves Differentially Affects Dietary Fat Intake in Obesity-Prone and Obesity-Resistant Rats

The current prevalence of obesity has been linked to the consumption of highly palatable foods and may be mediated by a dysregulated or hyposensitive orosensory perception of dietary fat, thereby contributing to the susceptibility to develop obesity. The goal of the current study was to investigate the role of lingual taste input in obesity-prone (OP, Osborne-Mendel) and obesity-resistant (OR, S5B/Pl) rats on the consumption of a high-fat diet (HFD). Density of fungiform papillae was assessed as a marker of general orosensory input. To determine if orosensory afferent input mediates dietary fat intake, surgical transection of the chorda tympani and glossopharyngeal nerves (GLX/CTX) was performed in OP and OR rats and HFD caloric intake and body weight were measured. Fungiform papillae density was lower in OP rats, compared with OR rats. GLX/CTX decreased orosensory input in both OP and OR rats, as measured by an increase in the intake of a bitter, quinine solution. Consumption of low-fat diet was not altered by GLX/CTX in OP and OR rats; however, GLX/CTX decreased HFD intake in OR, without altering HFD intake in OP rats. Overall, these data suggest that inhibition of orosensory input in OP rats do not decrease fat intake, thereby supporting that idea that hyposensitive and/or dysregulated orosensory perception of highly palatable foods contribute to the susceptibility to develop obesity.

Isolation of a Pseudomonas sp. Which Utilizes the Phosphonate Herbicide Glyphosate

A strain of bacteria has been isolated which rapidly and efficiently utilizes the herbicide glyphosate (N-phosphonomethylglycine) as its sole phosphorus source in a synthetic medium. The strain (PG2982) was isolated by subculturing Pseudomonas aeruginosa ATCC 9027 in a synthetic broth medium containing glyphosate as the sole phosphorus source. Strain PG2982 differs from the culture of P. aeruginosa in that it is nonflagellated, does not produce pyocyanin, and has an absolute requirement for thiamine. Strain PG2982 has been tentatively identified as a Pseudomonas sp. strain by its biochemical activities and moles percent guanine plus cytosine. Measurements of glyphosate with an amino acid analyzer show that glyphosate rapidly disappears from the medium during exponential growth of strain PG2982. In batch culture at 30 degrees C, this isolate completely utilized 1.0 mM glyphosate in 96 h and yielded a cell density equal to that obtained with 1.0 mM phosphate as the phosphorus source. However, a longer lag phase and greater generation time were noted in the glyphosate-containing medium. Strain PG2982 can efficiently utilize glyphosate as an alternate phosphorus source.

Constitutive activation of STAT-3 and downregulation of SOCS-3 expression induced by adrenalectomy

Removal of adrenal steroids by adrenalectomy (ADX) slows or reverses the development of many forms of obesity in rodents, including those that are leptin or leptin receptor deficient. Obesity is associated with hyperleptinemia and leptin resistance. We hypothesized that glucocorticoids impair leptin receptor signaling and that removal thereof would activate the Janus kinase (JAK)-signal transducers and activators of transcription (STAT) signaling pathway. The inhibitory effect of leptin (2.5 microg icv) on food intake was enhanced in ADX rats. A combination of ribonuclease protection assays, RT-PCR, Western blots, and mobility shift assays was used to evaluate the leptin signaling pathway in whole hypothalami from sham-operated, ADX and corticosterone-replaced ADX (ADX-R) Sprague-Dawley rats that were treated acutely with either saline vehicle or leptin intracerebroventricularly. ADX increased the expression of leptin receptor mRNA, increased STAT-3 mRNA and protein levels, induced constitutive STAT-3 phosphorylation and DNA binding activity, and also reduced suppressor of cytokine signaling-3 (SOCS-3) mRNA and protein levels. ADX and leptin treatment increased STAT-3 phosphorylation, but with no concomitant increase in DNA binding activity. Leptin and ADX decreased NPY mRNA expression, but their combination did not further decrease NPY mRNA. Corticosterone supplementation of ADX rats partially reversed many of these effects. In conclusion, ADX through activation of STAT-3 and inhibition of SOCS-3 activates the JAK-STAT signaling pathway. These effects most probably explain the ability to prevent the development of obesity by removal of adrenal steroids.

The effects of a high fat diet on leptin mRNA, serum leptin and the response to leptin are not altered in a rat strain susceptible to high fat diet-induced obesity

Osborne-Mendel (OM) and S5B/Pl rats differ in their sensitivity to develop obesity when fed a high fat (HF) diet; OM rats become obese, whereas S5B/Pl rats remain thin. We have investigated the possibilities that either an impaired leptin response or resistance to leptin action underlies the sensitivity to this form of obesity in OM rats. In Experiment 1, OM and S5B/Pl rats fed a nonpurified diet were killed at d 0 or were fed either a HF (56% fat energy) or a low fat (LF, 10% fat energy) diet for 2 or 7 d. The HF diet increased serum leptin significantly by d 2 to levels that were similar in both rat strains. At 7 d, leptin levels were lower than at d 2 but remained higher than levels in the d 0 control groups. The leptin mRNA:18S RNA ratio in epididymal adipose tissue increased to higher levels in HF-fed OM rats than in S5B/Pl rats fed that diet. However, although the LF diet had no effect in S5B/Pl rats, it increased leptin mRNA levels in epididymal adipose tissue of OM rats compared with the controls fed the nonpurified diet. In Experiment 2, OM and S5B/Pl rats were fed HF or LF diets for 5 wk. At that time, their feeding response to a range of leptin doses (0, 1, 5 or 10 microgram) given intracerebroventricularly was tested after overnight food deprivation. There was a similar dose-dependent reduction in energy intake in response to leptin in both OM and S5B/Pl rats. These responses were independent of the diet. The data suggest that the susceptibility of OM rats to HF diet-induced obesity is not related to either a loss of central sensitivity to leptin or a failure to enhance leptin production acutely, although the failure to maintain chronically increased levels of serum leptin could contribute to the obesity.

Differential expression of insulin receptor tyrosine kinase inhibitor (fetuin) gene in a model of diet-induced obesity

The Differential Display technique has been used to identify differences in mRNA expression in adipose tissue after the introduction of a high fat diet to two strains of rat (OM and S5B/PI) that differ in their susceptibility to develop obesity on this diet. The insulin receptor tyrosine kinase inhibitor protein (fetuin) was shown to be differentially expressed in OM but not S5B/PI rats. This circulating protein may play a role in the development of peripheral insulin resistance associated with high fat diets.

Evidence of participation of McrB(S) in McrBC restriction in Escherichia coli K-12

The McrBC restriction system has the ability to restrict DNA containing 5-hydroxymethylcytosine, N4-methylcytosine, and 5-methylcytosine at specific sequences. The mcrB gene produces two gene products. The complete mcrB open reading frame produces a 51-kDa protein (McrB(L)) and a 33-kDa protein (McrB(S)). The smaller McrB polypeptide is produced from an in-frame, internal translational start site in the mcrB gene. The McrB(S) sequence is identical to that of McrB(L) except that it lacks 161 amino acids present at the N-terminal end of the latter protein. It has been suggested that McrB(L) is the DNA binding restriction subunit. The function of McrB(S) is unknown, although there has been speculation that it plays some role in the modulation of McrBC restriction. Studies of the function of McrB(S) have been challenging since it is produced in frame with McrB(L). In this study, we tested the effects of underproduction (via antisense RNA) and overproduction (via gene dosage) of mcrBC gene products on restriction levels of the mcrBC+ strain JM107. Among the parameters monitored was the induction of SOS responses, which indicate of DNA damage. Evidence from this study suggests that McrB(S) is necessary for stabilization of the McrBC restriction complex in vivo.

Differences in binding of hepatic nuclear proteins from lean and obese rats to the 5'-upstream region of tyrosine aminotransferase

The glucocorticoid effects on liver tyrosine aminotransferase mRNA levels have been studied in young, lean, and obese Zucker (fa/fa) rats and 5'-upstream regions of the tyrosine aminotransferase (TAT) gene have been used in gel retardation studies to investigate nuclear protein binding. Hepatic TAT mRNA levels were increased in obese fa/fa rats but were normalized seven days after adrenalectomy. Corticosterone replacement to adrenalectomized rats restored the increased levels of TAT mRNA in the obese animals. A 60-bp fragment of upstream TAT DNA (-2463 to -2403) was identified which showed higher levels of band shifting after incubation with hepatic nuclear proteins of obese rats compared with the proteins from lean animals. This differential level of gel retardation was substantially reduced by alkaline phosphatase treatment of nuclear proteins. Gel retardation was reduced when nuclear proteins were prepared from adrenalectomized obese rats, and increased with nuclear proteins from adrenalectomized rats replaced with corticosterone. DNA affinity chromatography and gel electrophoresis identified three proteins of approximately 58, 62, and 65 kDa in the DNA-protein complex. Increased amounts of these three proteins were purified from nuclei of obese rats. HNF3 alpha antibodies induced hypershift of the gel retardation pattern implicating HNF3 alpha as one of the proteins that binds to the 60 bp DNA fragment. The data support the hypothesis that decreased phosphorylation of nuclear proteins in obese rats is glucocorticoid-dependent and may contribute to the altered transcriptional activity of glucocorticoid-responsive genes.

Purification and N-terminal amino acid sequences of two polypeptides encoded by the mcrB gene from Escherichia coli K-12

This report provides a purification method for the two proteins, 51 kDa and 33 kDa, both encoded by the same mcrB gene of the McrBC restriction system in Escherichia coli K-12. The two proteins were produced in large quantity using a T7 expression system and copurified to near homogeneity by DEAE-Sepharose and Affi-Gel blue column chromatography. The N-terminal amino acid sequences of these purified McrB proteins were the same as those predicted from the mcrB DNA sequence by Ross et al. [J. Bacteriol. 171 (1989b) 1974-1981]. The 33-kDa protein totally overlaps the C-terminal part of the 51-kDa protein.

DNA restriction polymorphism in wild isolates of Spodoptera frugiperda nuclear polyhedrosis virus

Restriction endonuclease analysis was used to examine variation in DNA of 22 wild isolates of Spodoptera frugiperda nuclear polyhedrosis virus (SfNPV). Eleven of the 15 isolated from Louisiana were distinguishable based on restriction fragment profiles from the enzymes BamHI, HindIII, and EcoRI. There was significant genetic variation in SfNPV isolates within single agricultural fields. Nucleotide sequence divergence values, based on restriction fragment profiles, indicated that genetic variation among isolates foreign to Louisiana (Ohio, Ecuador, Mexico, Georgia, Colombia, and Venezuela) was greater than that among the Louisiana isolates. However, certain foreign isolates were similar to or identical with Louisiana isolates. Genetic variation of the viral DNA was not influenced by the insect's host plan species.

Overproduction and purification of McrC protein from Escherichia coli K-12

The McrC protein, encoded by one of the two genes involved in the McrB restriction system, was produced in Escherichia coli cells by using a T7 expression system. Following sequential DEAE-Sepharose and hydroxylapatite column chromatography, the protein was purified to apparent homogeneity as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The N-terminal amino acid sequence of the purified McrC protein agreed exactly with the one deduced from the DNA sequence by Ross et al. (J. Bacteriol. 171:1974-1981, 1989).

Nomenclature relating to restriction of modified DNA in Escherichia coli

At least three restriction systems that attack DNA containing naturally modified bases have been found in common Escherichia coli K-12 strains. These systems are McrA, McrBC, and Mrr. A brief summary of the genetic and phenotypic properties so far observed in laboratory strains is set forth, together with a proposed nomenclature for describing these properties.

Cloning of a gene from Pseudomonas sp. strain PG2982 conferring increased glyphosate resistance

A plasmid carrying a 2.4-kilobase-pair fragment of DNA from Pseudomonas sp. strain PG2982 has been isolated which was able to increase the glyphosate resistance of Escherichia coli cells. The increase in resistance was dependent on the presence of a plasmid-encoded protein with a molecular weight of approximately 33,000, the product of a translational fusion between a gene on the vector, pACYC184, and the insert DNA. An overlapping region of the PG2982 chromosome carrying the entire gene (designated igrA) was cloned, and a plasmid (pPG18) carrying the gene was also able to increase glyphosate resistance in E. coli. A protein with a molecular weight of approximately 40,000 was encoded by the PG2982 DNA contained in pPG18. This plasmid was not able to complement a mutation in the gene for 5-enolpyruvylshikimate-3-phosphate synthase (aroA) in E. coli, and modification of glyphosate by E. coli cells containing the plasmid could not be demonstrated. The nucleotide sequence of the PG2982 DNA contained an open reading frame able to encode a protein with a calculated molecular weight of 39,396.

Serratia marcescens rpr gene sensitizes Escherichia coli wild-type, xth, and nfo strains to methyl methanesulphonate

It is reported here that the rpr DNA repair gene of Serratia marcescens does not complement an Escherichia coli xth nfo AP endonuclease mutation for resistance to methyl methanesulphonate (MMS). Rather, rpr sensitized Escherichia coli wild-type, xth, and nfo strains to MMS. Also, it was found that rpr could not complement a triple tag alkA recA mutation in E. coli, indicating that there are limits to rpr complementing capabilities. It was determined that rpr gene dosage was not a factor in recA complementation. MMS sensitization of an E. coli wild-type strain, however, was directly related to rpr copy number. These data indicate that Rpr does not have an associated AP endonuclease activity, and that it is incapable of substituting for Tag I, Tag II, and RecA in a tag alkA recA background.

Evidence for unique DNA repair activity encoded by a cloned Serratia marcescens gene: suppression of Escherichia coli mutations that reduce repair of alkylated DNA

A recombinant plasmid containing a Serratia marcescens DNA repair gene has been analyzed biochemically and genetically in Escherichia coli mutants deficient for repair of alkylated DNA. The cloned gene suppressed sensitivity to methyl methanesulfonate of an E. coli strain deficient in 3-methyladenine DNA glycosylases I and II (i.e., E. coli tag alkA) and two different E. coli recA mutants. Attempts to suppress the methyl methanesulfonate sensitivity of the E. coli recA mutant by using the cloned E. coli tag and alkA genes were not successful. Southern blot analysis did not reveal any homology between the S. marcescens gene and various known E. coli DNA repair genes. Biochemical analysis with the S. marcescens gene showed that the encoded DNA repair protein liberated 3-methyladenine from alkylated DNA, indicating that the DNA repair molecular is an S. marcescens 3-methyladenine DNA glycosylase. The ability to suppress both types of E. coli DNA repair mutations, however, suggests that the S. marcescens gene is a unique bacterial DNA repair gene.

Identification of a second polypeptide required for McrB restriction of 5-methylcytosine-containing DNA in Escherichia coli K12

The McrB restriction system in Escherichia coli K12 causes sequence-specific recognition and inactivation of DNA containing 5-methylcytosine residues. We have previously located the mcrB gene near hsdS at 99 min on the E. coli chromosome and demonstrated that it encodes a 51 kDa polypeptide required for restriction of M.AluI methylated (A-G-5mC-T) DNA. We show here, by analysis of maxicell protein synthesis of various cloned fragments from the mcrB region, that a second protein of approximately 39 kDa is also required for McrB-directed restriction. The new gene, designated mcrC, is adjacent to mcrB and located distally to hsdS. The McrB phenotype has been correlated previously with restriction of 5-hydroxy-methyl-cytosine (HMC)-containing T-even phage DNA that lacks the normal glucose modification of HMC, formally designated RglB (for restriction of glucoseless phage). This report reveals a difference between the previously correlated McrB and RglB restriction systems: while both require the mcrB gene product only the McrB system requires the newly identified mcrC-encoded 39-kDa polypeptide.

Nucleotide sequence of the McrB region of Escherichia coli K-12 and evidence for two independent translational initiation sites at the mcrB locus

The McrB restriction system of Escherichia coli K-12 is responsible for the biological inactivation of foreign DNA that contains 5-methylcytosine residues (E. A. Raleigh and G. Wilson, Proc. Natl. Acad. Sci. USA 83:9070-9074, 1986). Within the McrB region of the chromosome is the mcrB gene, which encodes a protein of 51 kilodaltons (kDa) (T. K. Ross, E. C. Achberger, and H. D. Braymer, Gene 61:277-289, 1987), and the mcrC gene, the product of which is 39 kDa (T. K. Ross, E. C. Achberger, and H. D. Braymer, Mol. Gen. Genet., in press). The nucleotide sequence of a 2,695-base-pair segment encompassing the McrB region was determined. The deduced amino acid sequence was used to identify two open reading frames specifying peptides of 455 and 348 amino acids, corresponding to the products of the mcrB and mcrC genes, respectively. A single-nucleotide overlap was found to exist between the termination codon of the mcrB gene and the proposed initiation codon of the mcrC gene. The presence of an additional peptide of 33 kDa in strains containing various recombinant plasmids with portions of the McrB region has been reported by Ross et al. (Gene 61:277-289, 1987). The analysis of frameshift and deletion mutants of one such hybrid plasmid, pRAB-13, provided evidence for a second translational initiation site within the McrB open reading frame. The proposed start codon for translation of the 33-kDa peptide lies 481 nucleotides downstream from the initiation codon for the 51-kDa mcrB gene product. The 33-kDa peptide may play a regulatory role in the McrB restriction of DNA containing 5-methylcytosine.

Molecular cloning and characterization of a genetic region from Serratia marcescens involved in DNA repair

We report here the molecular isolation of a DNA fragment which encodes Tag-like activity from the Gram-negative bacterium Serratia marcescens. A recombinant plasmid encoding Tag-like activity was isolated from a S. marcescens plasmid gene library by complementation of an Escherichia coli tag mutant, which is deficient in 3-methyladenine DNA glycosylase I. The clone complements E. coli tag, recA, alkA, but not alkB, mutants for resistance to the DNA-damaging agent methyl methanesulphonate (MMS). The coding region of the Tag activity, initially isolated on a 6.5kb BamHI fragment, was defined to a 1.8kb BglII-SmaI fragment. Labelling of plasmid-encoded proteins using maxicells revealed that the 1.8kb fragment encodes two proteins of molecular weights 42,000 and 16,000. Data presented here suggest that the cloned fragment encodes a DNA repair protein(s) that has similar activity to the 3-methyladenine DNA glycosylase I of E. coli.

Phosphate starvation induces uptake of glyphosate by Pseudomonas sp. strain PG2982

Pseudomonas sp. strain PG2982 has the ability to use the phosphonate herbicide, glyphosate, as a sole phosphorus source (J. K. Moore, H. D. Braymer, and A. D. Larson, Appl. Environ. Microbiol. 46:316-320, 1983). Glyphosate uptake is maximal in the late log phase of growth and is induced by phosphate starvation. Uptake is inhibited by phosphate and arsenate, but not by the amino acids glycine and sarcosine. The Km and Vmax for glyphosate uptake were calculated to be 23 microM and 0.97 nmol/mg (dry weight) per min, respectively. A phosphate transport system with a broad substrate specificity may be responsible for glyphosate uptake.

Organization and sequence of the hsd genes of Escherichia coli K-12

The nucleotide sequence of the hsdR and M genes, together with that for hsdS comprises an 8400 base segment spanning the entire hsd region of Escherichia coli K-12. The three hsd genes are transcribed in the same direction, but from two promoters. hsdR and hsdM are separated by 492 base-pairs, whereas the termination codon of hsdM overlaps the initiation codon of hsdS. pres precedes hsdR, and our data indicate a transcription termination signal in the interval between hsdR and pmod, as expected if transcription of hsdM and S is dependent on pmod. Transcription from pres is not influenced by the products of the hsdM and S genes, and the mechanism whereby restriction is prevented when the hsd region is transferred to a modification-deficient cell remains to be elucidated. A segment of the predicted amino acid sequence of the M polypeptide shares homology with a variety of adenine methylases and may identify part of the active site for methylation of specific adenine residues. The R polypeptide shows homology with a variety of ATPases, and pronounced regions of alpha-helical structure are predicted, one of which is amphipathic.

Localization of a genetic region involved in McrB restriction by Escherichia coli K-12

A 5,500-base-pair BglII-EcoRI fragment proximal to the hsd genes of Escherichia coli K-12 has been cloned in the plasmid vector pUC9. The resultant hybrid plasmid was shown to complement the mcrB mutation of E. coli K802. The presence of the hybrid plasmid in strain K802 caused an 18.3-fold drop in transformation efficiency with AluI-methylated pACYC184 relative to unmethylated pACYC184. These results indicate that the cloned DNA is involved in the McrB system restriction of 5-methylcytosine DNA.

Characterization of the Escherichia coli modified cytosine restriction (mcrB) gene

The McrB restriction system of Escherichia coli K-12 is responsible for the inactivation of 5-methylcytosine-containing DNA. The mcrB mutation of E. coli strain K802 was complemented by hybrid plasmid pUC9-14 which consists of a 5.5-kb Bg/II-Eco RI fragment from the E. coli K-12 chromosome cloned in pUC9 (Ross and Braymer, 1987). The limits of the mcrB gene within the 5.5-kb insert were defined by deleting portions the fragment and assaying for McrB restriction of M. AluI-methylated DNA. A 51-kDa polypeptide was identified as the mcrB gene product based on an analysis of maxicell-labeled polypeptides from pUC9-14 and deletion derivatives of this plasmid. Deletion analyses and transcription initiation assays enabled us to determine the direction of transcription and translation of mcrB. Transcription initiates approx. 710 bp beyond the end of the hsdS gene, and proceeds in the same direction as the transcription of the hsdR, hsdM, and hsdS genes, which is clockwise on the conventional E. coli map.

Glyphosate catabolism by Pseudomonas sp. strain PG2982

The pathway for the degradation of glyphosate (N-phosphonomethylglycine) by Pseudomonas sp. PG2982 has been determined by using metabolic radiolabeling experiments. Radiorespirometry experiments utilizing [3-14C]glyphosate revealed that approximately 50 to 59% of the C-3 carbon was oxidized to CO2. Fractionation of stationary-phase cells labeled with [3-14C]glyphosate revealed that from 45 to 47% of the assimilated label is distributed to proteins and that the amino acids methionine and serine are highly labeled. Adenine and guanine received 90% of the C-3 label found in the nucleic acid fraction, and the only pyrimidine base labeled was thymine. These results indicated that C-3 of glyphosate was at some point metabolized to a C-1 compound whose ultimate fate could be both oxidation to CO2 and distribution to amino acids and nucleic acid bases that receive a C-1 group from the C-1-donating coenzyme tetrahydrofolate. Pulse-labeling of PG2982 cells with [3-14C]glyphosate resulted in the isolation of [3-14C]sarcosine as an intermediate in glyphosate degradation. Examination of crude extracts prepared from PG2982 cells revealed the presence of a sarcosine-oxidizing enzyme that oxidizes sarcosine to glycine and formaldehyde. These results indicate that the first step in glyphosate degradation by PG2982 is cleavage of the carbon-phosphorus bond, resulting in the release of sarcosine and a phosphate group. The phosphate group is utilized as a source of phosphorus, and the sarcosine is degraded to glycine and formaldehyde. This pathway is supported by the results of [1,2-14C]glyphosate metabolism studies, which show that radioactivity in the proteins of labeled cells is found only in the glycine and serine residues.

Phosphonate Utilization by the Glyphosate-Degrading Pseudomonas sp. Strain PG2982

The glyphosate-degrading Pseudomonas sp. strain PG2982 was found to utilize each of 10 organophosphonate compounds as a sole phosphorus source. Representative compounds tested included alkylphosphonates, 1-amino-substituted alkylphosphonates, amino-terminal phosphonates, and an arylphosphonate. This report demonstrates that PG2982 is capable of utilizing a wider range of structurally different organophosphonate compounds than any organism described to date.

Nitrogen fixation system of tungsten-resistant mutants of Azotobacter vinelandii

Mutants of Azotobacter vinelandii ATCC 12837 were isolated which could fix N2 in the presence of high tungsten concentrations. The most studied of these mutants (WD2) grew well in N-free modified Burk broth containing 10 mM W, whereas the wild type would not grow in this medium. WD2 would also grow in Burk N-free broth at about the same rate as the wild type. WD2 in broth containing W exhibited 22% of the whole cell acetylene reduction activity of the wild type in broth containing Mo and showed a lowered affinity for acetylene. Two-dimensional gel electrophoresis experiments showed that N2-fixing cells of WD2 from broth containing W or Mo did not produce significant amounts of component I of native nitrogenase protein. Electron spin resonance spectra of whole cells and cell-free extracts of WD2 from broth containing W lacked any trace of the g = 3.6 resonance associated with FeMoCo.

Purification and characterization of the extracellular proteinase of Serratia marcescens

The extracellular proteinase produced by a depressed strain of Serratia marcescens ATCC 25419 was purified and characterized. This produces more than 10-times the amount of extracellular proteinase produced by other strains of Serratia tested. The purified enzyme was prepared from the culture supernatant by (NH4)2SO4 fractionation and DEAE-cellulose chromatography. The purified enzyme has an so20,w of 3.95 and is a monomer of molecular weight 51,900. The proteinase has a broad pH optimum in the alkaline range with a maximum at pH 9.5. The enzyme will utilize a number of proteins as substrate. The products of digestion are primarily in the size range of tripeptides to hexapeptides. Peptides containing a sensitive bond and a minimum size of size amino acids are hydrolyzed. The proteinase is inhibited by chelating agents but unaffected by sulfhydryl or serine reagents and is devoid of esterase activity.

Purification of the protein employed in an immunodiffusion test to diagnose infectious bovine rhinotracheitis

The antigen used in an immunodiffusion test to diagnose infectious bovine rhinotracheitis has been purified by affinity chromatography. The homogeneity of the antigen was indicated by sedimentation rate and sedimentation equilibrium experiments. A So20,w of 0.749 was determined and a molecular weight of 8900 was calculated from sedimentation equilibrium analysis. The purified antigen formed precipitin lines of identity with crude diagnostic antigen. Purified antigen remained serologically active in the immunodiffusion test after lyophilization and subsequent reconstitution.

Purification, characterization, and quantitation of the antigen employed in the immunodiffusion test for diagnosis of equine infectious anemia

Equine infectious anemia (EIA) antigen extracted from the spleen of horses infected with EIA virus was purified by pH treatment, (NH4)2SO4 fractionation and affinity chromatography. The homogeneity of the antigen was indicated by sedimentation rate and sedimentation equilibrium experiments. A S20,w of 0.51 was determined and a molecular weight of 7600 was calculated from sedimentation equilibrium analysis. The amino acid composition of the pure antigen indicated the antigen is an acidic protein. Employing radical immunodiffusion (RID) and pure antigen a method for quantitating antigen content of antigen containing preparations was developed.

Neurospora crassa invertase. A study of amino acids at the active center

1. The effects on Neurospora crassa invertase (beta-D-fructofuranoside fructohydrolase, EC 3.2.1.26) of a variety of group specific reagnets and other potential inhibitors were determined during a search for an irreversible inhibitor of the enzyme. Aniline, pyridoxal, enzyme substrate and products did not inactivate invertase under reducing conditions. Bromoacetic acid, iodoacetic acid, iodoacetamide, p-chloromercuribenzoate, hydroxylamine and 2-hydroxy-5-nitrobenzyl bromide were also ineffective. Iodine was the only reagent which irreversibly inhibited invertase. 2. Invertase was rapidly inactivated by low concentrations of iodine, indicating specific inhibition. However, the enzyme could not be protected from this inactivation by substrate. It was not reactivated by mercaptoethanol or cysteine. 3. Experiments on the uptake of radioactive iodine demonstrated that invertase is not iodinated under the conditions of iodine inactivation. 4. The sedimentation (S20,w) value of invertase was not altered by iodine inactivation. One-dimensional electrophoresis and finger-printing of tryptic digests revealed no differences between iodine treated and untreated invertase. There was no loss of carbohydrate from this glycoprotein during iodine inactivation. 5. Standard amino acid analyses of iodine-inactivated invertase showed some loss of tyrosine and a trace amount of methionine sulfone. Attempts to demonstrate oxidation of methionine to the sulfone, through modification of the procedure for preparation of samples for analysis, were unsuccessful. However, oxidation of half-cystine was indicated and further loss of tyrosine noted. A hypothesis is advanced that half-cystine is oxidized by iodine to a normally unstable oxidation state which is maintained and protected by its protein invironment and that loss of tyrosine may be an artifact caused by the presence of this residue during acid hydrolysis.