Identification and amino acid sequence of the deoxynucleoside triphosphate binding site in Escherichia coli DNA polymerase I

We have labeled the large fragment of Escherichia coli DNA polymerase I (Pol I) with pyridoxal 5'-phosphate, a substrate binding site directed reagent for DNA polymerases [Modak, M. J. (1976) Biochemistry 15, 3620-3626]. A covalent attachment of pyridoxal phosphate to Pol I results in the loss of substrate binding as well as the polymerase activity. The inactivation was found to be strictly dependent on the presence of a divalent metal ion. Four moles of pyridoxal phosphate was found to react per mole of the enzyme, while in the presence of substrate deoxynucleoside triphosphate only 3 mol of pyridoxal phosphate was bound. To identify the substrate-protected site on the enzyme, tryptic peptides from enzyme labeled with pyridoxal phosphate and tritiated borohydride, in the presence and absence of substrate, were resolved on a C-18 reverse-phase column. A single peptide containing the substrate-protected site was identified and further purified. The amino acid composition and sequence analysis of this peptide revealed it to span residues 756-775 in the primary acid sequence of Pol I. Lys-758 of this sequence was found to be the site of the pyridoxal phosphate reaction. It is therefore concluded that Lys-758 is the site of binding for the metal chelate form of nucleotide substrates in E. coli DNA polymerase I.

An affinity labeling of ras p21 protein and its use in the identification of ras p21 in cellular and tissue extracts

We have carried out photoaffinity labeling of the ras p21 protein, a ras oncogene product, with [alpha-32P]GTP. Based on our studies, a sensitive, rapid, and specific assay for the detection of multiple forms of ras p21 has been developed. The specificity of this protocol is shown by (a) sensitivity of affinity labeling of ras p21 to known inhibitors of GTP binding and (b) immunoprecipitation of affinity labeled protein with anti-ras p21 serum. Detection and semiquantitation of ras p21 by this method is accomplished in less than 24 h and requires as little as 100,000 cells or about 5 mg of tissue sample from skin tumor, liver, and mammary tumor tissues. Furthermore, using this approach, we were able to detect the selective loss of one species of ras p21 in transplanted Morris hepatoma cells.

Binding of an antagonistic monoclonal antibody to an intact and fragmented EGF-receptor polypeptide

A murine monoclonal antibody (No. 425) raised against human A431 carcinoma cells specifically immunoprecipitates the 170,000 molecular weight epidermal growth factor (EGF)-receptor from extracts of A431 cells as well as from extracts of human placenta and cultured fibroblasts, but does not recognize the murine receptor. Binding to the external domain of the human EGF-receptor was indicated by indirect immunofluorescent staining of fixed nonpermeable cells. The antibody binds to both glyco- and aglycoreceptor forms, indicating that the epitope is a part of the polypeptide chain. Binding of the antibody to the receptor is conformation dependent; i.e., denatured receptors lacking EGF-binding activity are not recognized by the antibody. The results of antibody binding studies indicate that the epitope is closely linked to the EGF binding active site, and is common to both high- and low-affinity EGF-receptors. Interaction of this epitope with the antibody inhibits EGF binding and bioactivity, and triggers receptor down-regulation, but does not generate EGFlike kinase-stimulatory or mitogenic responses either in vitro or in vivo. The antibody was tested for its ability to bind to domain-sized fragments of the 170-kDa EGF-receptor. It can recognize both the proteolytically generated 110-kDa EGF binding peptide, and a soluble 100-kDa EGF-receptor secreted by A431 cells. This indicates that the epitope recognized this antibody retains its conformation after proteolytic separation of the EGF binding domain from the rest of the receptor molecule.

Partial purification and characterization of Naegleria fowleri beta-glucosidase

Naegleria fowleri cells, grown axenically, contain high levels of beta-D-glucosidase which catalyzes the hydrolysis of 4-methylumbelliferyl-beta-D-glucopyranoside (4MUGlc) (Km, 0.9 mM), octyl-beta-D-glucoside (Km, 0.17 mM), and p-nitrophenyl-beta-D-glucopyranoside at relative rates of 1.00, 2.88, and 1.16, respectively (substrate concentration, 3.0 mM). When the amebae are subjected to freeze-thawing, sonication, and centrifugation (100,000 g, 1 h), 85% of the beta-glucosidase activity appears in the supernatant fraction. The beta-glucosidase was purified 40-fold (34% yield) using a combination of chromatographic steps involving DE-52 cellulose, concanavalin A-Sepharose, and hydroxylapatite followed by isoelectric focusing. The predominant soluble beta-D-galactosidase activity in the Naegleria extract copurifies with the beta-D-glucosidase; the two activities have the same isoelectric point (pI, 6.9), similar heat stabilities, are both inhibited by lactobionic acid (Ki, 0.40 mM), and exhibit optima at pH 4.5, indicating that they are probably the same enzyme. The Naegleria beta-D-glucosidase has an apparent molecular weight of 66,000, a Stokes radius of 25 A, and a sedimentation coefficient of 4.2S. The beta-glucosidase is not inhibited by conduritol beta-epoxide or galactosylsphingosine but is completely inhibited by 1.25 mM bromo conduritol beta-epoxide. The latter compound, when present in the growth medium, inhibits the growth of the organism and profoundly alters its ultrastructure, the main effect being the apparent inhibition of cytokinesis and the generation of multinucleate cells. The issue of the role of the beta-glucosidase in the metabolism of the ameba and its possible role in pathogenic mechanisms are discussed.

A genetic study among the Lepchas of the Darjeeling area of eastern India

A total of 215 Lepchas (75 Buddhists and 140 Christians) living in the Kalimpong subdivision, Darjeeling district, West Bengal, India, were investigated for the distribution of haemoglobin, serum proteins and red cell enzymes. The gene frequencies were as follows: HbE = 0.02; Hp1 = 0.18; TfB = 0.007; TfDChi = 0.005; Gc2 = 0.22; pa = 0.18; pc = 0.03; PGM2(1) = 0.18; PGM6(1) = 0.002; PGDc = 0.17; AK2 = 0.02; GLO1 = 0.21. The most striking features were the complete lack of G6PD deficiency and very high frequency of PGDC. The remaining loci (serum albumin, lactate dehydrogenase, malate dehydrogenase and glucose-6-phosphate dehydrogenase, phosphohexose isomerase and superoxide dismutase) were monomorphic. The gene frequencies were similar in the Buddhist and Christian Lepchas. The observed average heterozygosity (9 loci) was 0.20 in the entire sample.

Regulation of kinase and intermolecular bonding in intact and truncated epidermal growth factor receptor

Tyrosine kinase activity of the epidermal growth factor (EGF) receptor can be regulated by its state of association. Studies done with the purified receptor solubilized in Triton X-100 indicate that dimer formation results in negative regulation of kinase, whereas successive binding of EGF and ATP shift the association equilibrium toward the catalytically active monomeric form. The promotion of the monomeric state by ATP can be mimicked by various nonphosphorylating analogs indicating that nucleotide binding rather than autophosphorylation is responsible for stabilizing the monomeric receptor form. Truncated receptor forms, lacking either the external EGF-binding domain or the internal kinase (ATP-binding) domain, are unable to form stable dimers. These results suggest that both intra- and extracellular domains of the receptor act to stabilize the kinase-regulatory dimer.

Effects of altitude, ethnicity-religion, geographical distance, and occupation on adult anthropometric characters of eastern Himalayan populations

With a view to estimating the effect of altitude on body dimensions vis-à-vis ethnicity-religion, geographical distance, and occupation, a comprehensive multivariate statistical analysis was performed on data pertaining to 16 anthropometric characters collected from 1,103 individuals (643 males and 460 females) belonging to two ethnic groups-Sherpa and Lepcha. Samples were drawn from several locations in the eastern Himalayan region-Darjeeling and Kalimpong in West Bengal (India), and Nepal, situated at low (1,000-2,000 meters) and high (above 3,500 meters) altitudes. The individuals sampled practice different occupations and follow different religions. Significant age and sex effects were observed. The data were age-adjusted, and sexes were treated separately. A test of equality of mean vectors indicated heterogeneity among population groups. Almost all characters were found to contribute significantly to the ability to discriminate between the groups. The overall probability of correctly classifying an individual based on body dimensions into the group in which she or he actually belongs was high (between 0.64 and 0.77). Shape and size factors could be identified that explained about 50% of the total variance and yielded a reasonable separation of the groups. Results of four different types of multivariate statistical analyses were in agreement, and showed that altitude is most highly associated with body dimensions.

Sulfogalactocerebroside and bis-(monoacylglyceryl)-phosphate as activators of spleen glucocerebrosidase

Sequential extraction of human spleen membranes with sodium cholate and n-butanol removes endogenous lipids and renders glucocerebrosidase activity dependent upon exogenous acidic lipids (e.g., phosphatidylserine, gangliosides) and a heat-stable activator protein (HSF). In the present report, we show that two previously untested lysosomal acidic lipids, namely sulfogalactocerebroside and bis-(monoacylglyceryl)-phosphate (BMP), also activate normal human glucocerebrosidase. In addition, sulfogalactocerebroside also markedly enhanced the activity of glucocerebrosidase isolated from a patient with type 1 (non-neuronopathic) Gaucher's disease, resulting in a specific activity which was 60-80% that of control glucocerebrosidase. Furthermore, when the sulfolipid was used as the activator, glucocerebrosidase from the type 1 patient was 30 times more active than the corresponding glucocerebrosidase from a person with type 2 (neuronopathic) Gaucher's disease. In contrast, the two BMPs, one rich in C26 saturated fatty acid and another rich in C18 unsaturated fatty acids, were relatively poor activators of both mutant glucocerebrosidases while providing excellent reconstitution of control activity.

Comparison of the ability of phospholipids from rat liver lysosomes to reconstitute glucocerebrosidase

The in situ lipid activator of rat liver glucocerebrosidase was investigated. Rat liver lysosomes were purified (42.9-fold relative to the crude homogenate) by sequential isopycnic centrifugation in sucrose and metrizamide gradients. Lipids were extracted with chloroform:methanol (2:1) and phospholipids were separated by one-dimensional thin-layer chromatography. The phospholipid content of the lysosome preparation was 0.28 mumol lipid phosphorus/mg protein. Phosphatidylcholine was present as the major nonacidic phospholipid (39.3%). Of the acidic phospholipids, phosphatidylinositol and phosphatidylserine were present in the greatest amounts (12.0 and 19.7%, respectively). The resolved phospholipids were tested separately and in the presence of a heat-stable factor from Gaucher spleen for their ability to reconstitute butanol-delipidated rat liver glucocerebrosidase activity. Alone or in the presence of the heat-stable factor, phosphatidylserine and phosphatidylinositol were the most effective activators of glucocerebrosidase. Bis(monoacylglyceryl) phosphate derived from rat liver tritosomes or rabbit lung macrophages was also effective in reconstituting beta-glucosidase activity.

Comparison of N-acyl phosphatidylethanolamines with different N-acyl groups as activators of glucocerebrosidase in various forms of Gaucher's disease

The acidic phospholipid requirement of the predominant particulate beta-glucosidase of mammalian spleen and liver was investigated using a series of N-acyl derivatives of dioleoyl phosphatidylethanolamine (PE). The PE, a neutral phospholipid, was converted to an acidic lipid, (N-acyl)-phosphatidylethanolamine (NAPE) by acylation of the amino group with different fatty acyl chains. Lysosomal beta-glucosidases from rat liver and spleens of controls and patients with various types of Gaucher's disease were solubilized and delipidated by extraction with sodium cholate and 1-butanol. All members of the NAPE series tested were effective activators of the delipidated rat liver beta-glucosidase, and the stimulatory power of the NAPE family increased with increasing chain length of the fatty acid substitution. In contrast, dioleoyl-PE had no effect on beta-glucosidase activity. A heat-stable factor (HSF) purified from the spleen of a patient with Gaucher's disease significantly increased the sensitivity of the rat liver beta-glucosidase to all of the NAPE derivatives. The maximum stimulation achieved in the presence of HSF was independent of N-acyl chain length. Compared to the potent activator, phosphatidylserine (PS), (N-acetyl)-PE and (N-linoleoyl)-PE were half as effective as activators of beta-glucosidase from control human spleen. PS stimulated the beta-glucosidase of type 1 nonneurologic Gaucher's disease, but none of the NAPE compounds activated it. Neither PS nor any of the (N-acyl)-PE compounds could activate a delipidated preparation of beta-glucosidase obtained from the spleen of a neurologic case. These results indicate that although the presence of a net negative charge on a phospholipid confers upon it an ability to reconstitute beta-glucosidase activity to the normal, nonmutant enzyme, it is insufficient to permit differentiation of the various types of Gaucher's disease.

Characterization of the activation of rat liver beta-glucosidase by sialosylgangliotetraosylceramide

We show that sialosylgangliotetraosylceramide (GM1) is a potent activator of delipidated (sodium cholate- and 1-butanol-extracted) lysosomal rat liver glucocerebroside:beta-glucosidase. Stimulation of 4-methylumbelliferyl-beta-D-glucopyranoside hydrolysis by the beta-glucosidase was markedly dependent upon the concentration of GM1 in the assay medium. Estimations of critical micellar concentration (CMC) performed fluorometrically using the dye N-phenylnaphthylamine revealed two CMC values of GM1 above 18 degrees C; the CMC of the primary micelles (3.32 microM) was temperature-independent whereas that of the secondary micelles decreased with decreasing temperature (17.2 and 10.8 microM at 37 and 20 degrees C, respectively). In the temperature range of 18-39 degrees C, beta-glucosidase activity increased sharply when the GM1 concentration was above the CMC of the secondary micelles. Although a heat-stable factor, purified from the spleen of a patient with Gaucher's disease, had a profound effect on the activation of beta-glucosidase by GM1, it decreased the CMC only slightly (14.8 versus 17.2 microM at 37 degrees C). The heat-stable factor (8 micrograms/ml) changed the shape of the activation curve from sigmoidal to hyperbolic, suggesting that the heat-stable factor permits beta-glucosidase to be activated by primary micelles or monomers. The results of gel filtration chromatography and sucrose gradient centrifugation in H2O and D2O revealed that the activation of beta-glucosidase by GM1 was associated with an increase in the size of the enzyme from 45,800 to 178,500 daltons and an increase in the partial specific volume from 0.697 to 0.740 ml/g. The active, reconstituted beta-glucosidase appears to consist of 50% protein and 50% ganglioside (56 molecules/178,500 g). Concentrations of GM1 below the CMC of secondary micelles increased the rate of inactivation of the enzyme by the irreversible inhibitor conduritol B epoxide at 37 degrees C, indicating that GM1 monomers or primary micelles do interact with the enzyme, even though they do not increase the rate of hydrolysis of 4-methylumbelliferyl-beta-D-glucopyranoside by the enzyme.

Effects of membrane channel-forming polypeptides on mitochondrial oxidative phosphorylation. A comparison of alamethicin, gramicidin A, melittin and tetraacetyl melittin

Transmembrane channel-forming polypeptides can function as uncouplers of mitochondrial oxidative phosphorylation. The observed effects are dependent on the phosphate ion (Pi) concentration in the medium. At low Pi (2.5 mM) the order of uncoupling efficiencies is gramicidin A much greater than alamethicin greater than tetraacetyl melittin greater than melittin. The remarkably high activity of gramicidin A suggests insertion of preformed channel dimers into the membrane. It is also suggested that lipid phase association of peptides is necessary in the other cases. At Pi = 100 mM inhibitory effects are observed for alamethicin and tetraacetyl melittin. Less pronounced inhibition is seen for melittin, while no such effect is noted for gramicidin A. The site of inhibition is shown to be complex IV, and the differences in the behavior of the peptides are rationalized in terms of channel structures.

Observations on the suramin-mediated inhibition of cellular and viral DNA polymerases

We have examined the sensitivity of various cellular and viral DNA polymerases to Suramin, an antitrypanosomal drug, which has been reported to exhibit antireverse transcriptase activity. We find that Suramin is a nonspecific inhibitor of all the viral and cellular DNA polymerases, including terminal deoxynucleotidyl transferase, and that the inhibition is most readily reversed by the addition of serum albumin. The drug appears to bind to all the enzyme proteins with no apparent selectivity. Binding of Suramin to enzyme has been found to result in the loss of both substrate and templateprimer binding abilities of various enzymes, confirming the nonspecific nature of protein-Suramin interaction.

Study of ascorbate status in murine and human leukaemias

Since mice can synthesize ascorbic acid but man cannot, the ascorbate status in murine and human leukaemia was compared. The decline in plasma ascorbate concentration in both cases indicates that vitamin C deficiency occurs in malignancy. Analysis of tissue ascorbate values in mice also indicated that an enhanced rate of utilization of this vitamin occurs during malignancy, as does an increased rate of excretion, and both events may be responsible for vitamin C deficiency. The hepatic ascorbate values suggest an endeavour by the animals to compensate for the loss through increased synthesis and storage of the vitamin, at least in the early stages of the disease.

Further studies on the activation of glucocerebrosidase by a heat-stable factor from Gaucher spleen

Using Sephadex G-75 and DEAE-cellulose column chromatography, an 8270-Da glycopeptide (designated Fragment II) has been isolated from a cyanogen bromide-formic acid digest of a heat-stable factor from Gaucher spleen which activates a lipid-depleted preparation of lysosomal glucocerebrosidase from human liver. Fragment II contains all of the activity present in the native heat-stable factor. Compared with the parent factor, Fragment II contains four fewer cysteine and methionine residues and one less of each of the following: aspartic acid, threonine, serine, valine, isoleucine, and leucine. Nearly all of the monosaccharides present in the parent heat-stable factor can be accounted for in Fragment II, including three glucosamine, three mannose, one sialic acid, and one fucose. By itself, Fragment II has little or no stimulatory activity; its major effect is to markedly increase the sensitivity of glucocerebrosidase to activation by phosphatidylserine. A mixture of 1 microgram phosphatidylserine and 2 micrograms of the cyanogen bromide fragment activates the lipid-depleted preparation of glucocerebrosidase 50% more than 30 micrograms phosphatidylserine alone. Analysis of the Km and Vmax of glucocerebrosidase at various hydrogen ion concentrations revealed that the heat-stable factor and phosphatidylserine together dramatically increase the catalytic efficiency (Vmax/Km) of glucocerebrosidase while making apparent three ionizable groups that participate in the catalysis. Phosphatidylserine alone recruits two ionizable groups, but catalytic efficiency is lower than when heat-stable factor is also present. Heat-stable factor alone has no discernable effect on the ionization of functional groups on the enzyme or on catalytic efficiency. By sucrose density gradient ultracentrifugation, it was shown that preincubation of rat liver glucocerebrosidase with phosphatidylserine and heat-stable factor shifted the enzyme completely from a 56,600-Da form to a 188,100-Da form. The activity of the slower sedimenting form of glucocerebrosidase was totally dependent upon exogenous bile salt activator, whereas the faster sedimenting form exhibited the same activity in the presence or absence of sodium taurocholate. It appears that the heat-stable factor promotes the transfer of phosphatidylserine to glucocerebrosidase, which, in turn, results in an increase in both the catalytic efficiency and size of the enzyme.

Characterization of the phospholipid requirement of a rat liver beta-glucosidase

The lipid requirement of membrane-bound rat liver beta-glucosidase was investigated using 4-methylumbelliferyl-beta-D-glucopyranoside as the substrate. The enzyme was solubilized and delipidated by sequential extraction of a crude lysosomal fraction from rat liver lysosomes with sodium cholate and ice-cold butan-1-ol. Neither saturated nor unsaturated phosphatidylcholine activated this enzyme. In contrast, acidic phospholipids like phosphatidylglycerol (PtdGro) and phosphatidylserine (PtdSer) were effective activators. For the PtdGro series, fatty acid composition was important, with the shorter chain or unsaturated fatty acid-containing PtdGro species being the best activators. Heat-stable factor (HSF) from Gaucher spleen by itself (1-2 micrograms) had no effect on enzyme activity. However, the same amount of HSF when combined with 10 micrograms of PtdSer markedly stimulated beta-glucosidase activity. In the presence of HSF, di-9-cis-octadecenoyl-PtdGro (1 microgram) or -PtdSer (5 micrograms) provided maximum protection of beta-glucosidase against heat (60 degrees C) inactivation. In the absence of phospholipids, HSF had no effect on the rate of inactivation of the enzyme by the suicide inhibitor conduritol B epoxide (t0.5, 12 +/- 0.5 min); the maximum rate of inactivation was achieved in the presence of a mixture of PtdGro (2.5-5 micrograms) and HSF (t0.5, 2.8 min). The combination of PtdSer (10 micrograms) and HSF (1.3 micrograms) lowered the Km for 4-methylumbelliferyl-beta-D-glucopyranoside from 24 to 2.7 mM. Inhibition of the enzyme by the glucocerebrosidase substrate analogues N-hexyl-O-glucosylsphingosine and glucosylsphingosine was influenced by the activator substances. The inclusion of PtdSer and HSF in the beta-glucosidase assay medium lowered the Ki of N-hexyl-O-glucosylsphingosine 20-fold. The same combination of activators decreased the I0.5 of the enzyme for glucosylsphingosine from 89.4 to 7.6 microM. A study of log (Vmax./Km) versus pH indicated that the PtdSer-HSF pair creates the active site of beta-glucosidase, making apparent three ionizable groups on the enzyme with pK values in the range 4.5-5.1.

Evidence for repetitive structure of the large acyl-carrier protein subunit of Escherichia coli citrate lyase

The amino acid composition of the unusually large acyl-carrier protein subunit of citrate lyase from Escherichia coli is characteristic of a protein with a highly repetitive structure. Peptide mapping studies provide further evidence of repetitive sequences within the subunit. Only a single Pauly-positive spot is detected in the tryptic peptide map although the subunit contains 8 histidine residues. The 4 prosthetic groups covalently bound to the subunit are recovered in a single tryptic fragment in almost quantitative yield. These structural features of the large acyl-carrier protein subunit probably reflect internal gene duplications.

The effects of lanthanum chloride administration in newborn chicks on glutamate uptake and release by brain synaptosomes

Acute i.p. administration of lanthanum chloride to newborn chicks at a single dose of 250 mg/kg body weight causes inhibition of the high affinity uptake of [14C]glutamate by isolated brain synaptosomes. There is also a marked decrease in the release of preloaded [14C]glutamate from brain synaptosomes in the presence of externally available Ca2+ (1.2 mM) or a high K+ concentration (71 mM). The inhibition of glutamate release has been discussed in relation to depletion of Ca2+ binding to the synaptosomal membrane under lanthanum intoxication.

Activators of spleen glucocerebrosidase from controls and patients with various forms of Gaucher's disease

Glucocerebrosidase from normal human spleen, and spleen from cases of neurologic (types 2 and 3) and nonneurologic (type 1) Gaucher's disease, was delipidated and inactivated by extraction from membranes with sodium cholate and ice-cold 1-butanol. Control glucocerebrosidase was stimulated markedly by large quantities (20-30 micrograms/assay) of phosphatidylserine (PS), or by a combination of smaller amounts (1-2 micrograms) of PS and 3 micrograms of a heat-stable factor (HSF) derived from the spleen of a patient with Gaucher's disease. The residual glucocerebrosidase from a nonneurologic case, but not a neurologic case, was also responsive to PS and HSF. The combination of HSF and PS decreased the Km of the normal enzyme for 4-methylumbelliferyl-beta-D-glucopyranoside from 8.0 to 1.6 mM. These effectors also increased the reactivity of glucocerebrosidase to the inhibitor conduritol B epoxide; HSF alone had no effect (t1/2 = 19 +/- 0.5 min) whereas the maximum rate of inactivation (t1/2 = 4.0 min) by conduritol B epoxide was achieved in the presence of a mixture of PS (1 microgram) and HSF (3 micrograms). Phosphatidylglycerol (PG) and phosphatidic acid, also acidic phospholipids, were effective activators of glucocerebrosidase. Varying the fatty acid composition of PG had little effect on its ability to stimulate glucocerebrosidase activity. However, in the case of phosphatidylcholine (PC), a weaker activator than PG or PS, fatty acid composition had a significant impact on the ability of this neutral lipid to activate glucocerebrosidase; dilinoleoyl-PC and dicaproyl-PC were moderately effective activators, but distearoyl-PC and dioleoyl-PC were almost totally inactive. The mono-, and di-, and trisialogangliosides (GM1, GD1, and GT1 were less than half as effective as PS as activators of glucocerebrosidase. These results indicate that acidic phospholipids and the heat-stable factor may both play a role in explaining the genetic heterogeneity of Gaucher's disease.

S-acylated residues of the acyl-carrier protein subunit of Klebsiella aerogenes citrate lyase

Oxidation of the isolated deacetyl acyl-carrier protein subunit of citrate lyase from Klebsiella aerogenes with Cu2+-o-phenanthroline complex leads exclusively to intrapeptide disulfide bridge formation indicating that the cysteamine and the cysteine residues are located in close proximity. The S-acetylation of the cysteine residue in deacetyl acyl-carrier protein subunit is catalysed by a citrate lyase ligase preparation in presence of acetate and ATP. Reaction-inactivation of citrate lyase results in deacetylation of the S-acetyl cysteamine residue of the prosthetic group but not of the S-acylated cysteine residue in the acyl-carrier protein.

The presence of essential arginine residues at the active sites of citrate lyase complex from Klebsiella aerogenes

The acyl-transferase and acyl-lyase activities of Klebsiella aerogenes citrate lyase complex are inactivated by the arginine specific reagents phenylglyoxal and 2,3-butanedione, the former reagent being the more potent inhibitor. Citrate and (3S)-citryl-CoA protect the transferase activity, while acetyl-CoA markedly enhances the rate of the inactivation. (3S)-Citryl-CoA protects the lyase subunit in the complex from inactivation. The kinetics of inactivation suggest the involvement of a single arginine residue at each of the active sites of the transferase and of the lyase subunits.

Lysis of nitrofurantoin-resistant strain of Vibrio el tor

Both nitrofurantoin-sensitive and nitrofurantoin-resistant strains of Vibrio el tor were found to lyze in the presence of Tris-EDTA at alkaline pH. The rate of lysis was appreciably enhanced by lysozyme. The amounts of intracellular components, viz. proteins and carbohydrates, released from the nitrofurantoin-sensitive strain by Tris-EDTA treatment, were significantly lower than those from the nitrofurantoin-resistant strain. Differences in periplasmic proteins released from Tris-EDTA treated cells of nitrofurantoin-resistant and -sensitive strains were revealed by gel electrophoresis.

Neurotoxicity of lanthanum chloride in newborn chicks

Acute intraperitoneal administration of lanthanum chloride to newborn chicks at the single dose of 250 mg/kg body weight inhibits calcium binding to brain synaptosomal membrane. There is also marked depression in the activities of neural Ca2+-ATPase, Mg2+-ATPase, and cholinesterase after acute lanthanum chloride intoxication. The inhibition of these enzymes in relation to depletion of calcium binding to the synaptosomal membrane has been discussed.

Photoaffinity labeling of Klebsiella aerogenes citrate lyase by p-azidobenzoyl coenzyme A

p-Azidobenzoyl coenzyme A functions as a linear competitive inhibitor for (3S)-citryl-CoA in the citryl-CoA oxaloacetate-lyase reaction catalyzed by the Klebsiella aerogenes deacetylcitrate lyase complex (Ki = 80 microM; (3S)-citryl-CoA Km = 67 microM). Inactivation is irreversible on photolysis of p-azidobenzoyl-CoA in the presence of the deacetylcitrate lyase complex. Mg2+ is not required for the inactivation. Inactivation is blocked by (3S)-citryl-CoA in the presence of ethylenediaminetetraacetic acid. p-Azidobenzoyl-CoA has no effect on the acetyl-CoA:citrate CoA transferase activity of both the deacetylcitrate lyase complex and its isolated transferase subunit. The stoichiometry of the CoA ester binding has been investigated by the use of p-azido[14C]benzoyl-CoA as a photoaffinity reagent. The labeling is exclusively on the lyase beta subunit of the citrate lyase complex.

Lysozyme in Schwartz and Moloney virus-induced lymphoblastic leukaemia

Studies have been made on lysozyme in serum and tissue homogenates in normal and leukaemic mice. An increase in serum lysozyme level occurred in mice bearing both strains of leukaemia as compared to the normal counterparts. Moreover, the elevated enzyme levels seem to be related to the rise in neutrophils in peripheral blood. In the spleen and kidney of leukaemic mice, the lysozyme level was found to be lower than in the normals, while the enzyme level remained more or less unaltered in the liver. The findings are discussed in relation to other reports in the literature.

Variations in body dimensions in relation to altitude among the Sherpas of the eastern Himalayas

A biomedical study was undertaken on the Sherpas of Upper Khumbu (3500-4500m), Nepal, and their migrant counterparts in the lower altitudes (1000-1500m) of Kalimpong subdivision, Darjeeling district, West Bengal, to study the impact of altitude on human biological characteristics in this Himalayan population, following the basic design of the IBP/Human Adaptability Panel. The results of the anthropometric survey of the adults (234 males and 169 females) are presented here. The high-altitude Sherpas of both sexes have significantly higher values than their low-altitude counterparts for most of the length, breadth and girth measurements, weight, cormic index, weight/stature ratio, weight/(stature)2 ratio, chest/stature ratio, surface area and body fat.

Second- and higher-order waveguide grating filters. 1: Theory

A study of second- and higher-order waveguide grating filters is considerably complicated by the fact that the coupling between the guided waves and the radiated waves has to be taken into account. In this paper, we review the theoretical calculations of the spectral response of these grating filters that have been reported by several authors and present a new approach based on the use of the Green's functions of the waveguide structure. Excellent agreement is found between the results of our method of calculation and the results of other, more rigorous but much more complicated, methods. The Green's function method is thus a reasonably simple but fairly accurate method for calculating the spectral response of grating filters.

Second- and higher-order waveguide grating filters. 2: experiment

A series of careful and systematic measurements is made to determine the reflection, transmission, and radiation loss coefficients of second- and third-order waveguide grating filters, and the dependence of these coefficients on the wavelength of the incident light. The experimental measurements are found to agree very well with results of calculations made using a Green's function approach, which we have reported in the preceding paper. This shows the Green's function approach to be a reasonably simple but quite accurate method for calculating the spectral response of grating filters.

Malaria in the north-east of Scotland. A review of 31 cases (1974-78)

In recent years malaria has become the most common imported infection in the United Kingdom. This paper describes the 31 cases diagnosed in the North-East of Scotland between 1974 and 1978. Presentation of this disease in North-East Scotland, exceptional before 1974, has become more frequent recently-and this is largely due to the North Sea ‘oil boom’.

Random fluctuations in first-order waveguide grating filters

A simple method is proposed for studying the spectral response of a first-order waveguide grating filter with random fluctuations in the period of the grating. The method can be applied to any grating groove shape, and it can be used to study the effect of both random and systematic variations in other grating filter parameters. The numerical calculations using this model are simple to carry out, but may be time-consuming in some cases. Results are presented for grating filters with rectangular and triangular grooves.

Digital dermatoglyphics of three caste groups of Mysore

An analysis of digital pattern types and digital ridge counts was made for samples of three endogamous Mysore castes, viz., Lingayat, Vokkaliga and Adi Karnataka. The pattern types exhibit significant variations between Lingayat and Vokkaliga, and between Adi Karnataka and Vokkaliga, though, in general, distributional trend of the three principal pattern types are of the same order in all the three castes, having high frequency of loops, moderate whorls and low arches. In pattern types, differences between sexes are highly significant. The total ridge count (TRC) in both males and females is lower in the Adi Karnataka than in the Lingayat and Vokkaliga and the same holds good for the counts on each hand. Bimanual differences among the groups are small, and left hand counts in almost all the digits are consistently smaller than those of the right hand in all the castes irrespective of sex. TRC differences between sexes are not significant. It is striking that by contrast with the pattern type frequency data very little difference among the three Mysore castes emerges from the analysis of finger quantitative features, i.e., in total ridge count and pattern intensity index. Overall finger pattern frequencies of the present caste samples fit generally with those observed in other caste groups of Mysore but differ from the frequencies in Madras samples.

Un nouveau sérotype de Salmonella isolé au Canada: Salmonella montreal (431, 432: c: l,5)

A new serotype of Salmonella, Salmonella montreal (431, 432: c: 1,5) belonging to Kauffmann's sub-genus I was isolated from the faeces of a young male patient suffering from recurrent diarrhoea. [Journal translation]