Myotoxicity and physiological effects of three Trimeresurus flavoviridis phospholipases A2

When basic proteins I and II from Trimeresurus flavoviridis (Habu snake) venom, which are Lys-49-phospholipase A2 (PLA2) with low activity, were injected intramuscularly into mice, myonecrosis was induced accompanied by a rapid increase of plasma creatine kinase level. This increase was about 2 times greater than that raised by highly active T. flavoviridis Asp-49-PLA2 which has been regarded as a myotoxic factor. Calcium-dependent depolarization of frog muscle fibers was observed with basic proteins I and II but not with Asp-49-PLA2. Indirect hemolysis of rat erythrocytes was induced by Asp-49-PLA2 but not by basic proteins I and II. Myotoxicity and depolarization effects appear to be not necessarily related to lipolytic activity of proteins although hemolytic effects is in parallel to lipolytic potency. Light microscopic observations of muscle preparations treated with three PLA2s showed similar histological changes, i.e., myolytic necrosis without hemorrhage and infiltration of polymorphonuclear cells. The structural and functional elements of PLA2s for eliciting myotoxicity are discussed.

The alpha beta complexes of ATP synthase: the alpha 3 beta 3 oligomer and alpha 1 beta 1 protomer

The basic structures of the catalytic portion (F1, alpha 3 beta 3 gamma delta epsilon) of ATP synthase are the alpha 3 beta 3 hexamer (oligomer with cooperativity) and alpha 1 beta 1 heterodimer (protomer). These were reconstituted from the alpha and beta subunits of thermophilic F1 (TF1), and the alpha 3 beta 3 hexamer was crystallized. On electrophoresis, both the dimer and hexamer showed bands with ATPase activity. Using the dimer and hexamer, we studied the nucleotide-dependent rapid molecular dynamics. The formation of the hexamer required neither nucleotide nor Mg. The hexamer was dissociated into the dimer in the presence of MgADP, while the dimer was associated into the hexamer in the presence of MgATP. The hexamer, like mitochondrial F1 and TF1, showed two kinds of ATPase activity: one was cooperative and was inhibited by only one BzADP per hexamer, and the other was inhibited by three BzADP per hexamer.

Echocardiographic evaluation of pulmonary arterial hypertension in patients with progressive systemic sclerosis and related syndromes

In order to evaluate the usefulness of echocardiography in detection and characterization of pulmonary arterial hypertension (PAH) in scleroderma patients, we performed M-mode, two-dimensional, and Doppler echocardiography in 71 patients with progressive systemic sclerosis (PSS) and related syndromes: mixed connective tissue disease (MCTD) and overlap syndromes. We estimated systolic pressure gradients across the tricuspid valve from the peak velocity of tricuspid regurgitation (TR) by color-flow guided continuous wave Doppler. TR velocities of analyzable quality for gradient estimation were obtained in 28 patients (39%), of whom 12 showed PAH (peak TR velocity > or = 2.5 m/sec). In comparison, analyzable TR was recorded in 19 (35%) of 55 patients with left-sided cardiac disease. None of the 12 with Doppler-estimated PAH showed left ventricular dilatation or decreased fractional shortening by M-mode and two-dimensional measurements. Nonsimultaneous cardiac catheterization confirmed PAH in 8 of 9 with Doppler-estimated PAH and in 3 of 12 without analyzable TR who had hemodynamic study. Doppler-estimated right ventricular systolic pressures (RVSP) correlated well with catheterization-measured pulmonary arterial systolic pressures (PASP) (< 0.01). Our results indicate that Doppler echocardiography is useful in detecting subclinical PAH and estimating PASP in patients with collagen vascular disease. The results of pulmonary function studies suggest that PAH in MCTD is mainly caused by pulmonary vasculopathy.

Unusually high conservation of untranslated sequences in cDNAs for Trimeresurus flavoviridis phospholipase A2 isozymes

As a step toward understanding the structure and function of phospholipases A2 (PLA2s), we isolated and sequenced several cDNAs encoding Trimeresurus flavoviridis venom PLA2 isozymes including two [Lys49]PLA2s called basic proteins I and II, [Thr37]PLA2, and PLX'-PLA2. Comparison of the nucleotide sequences of these cDNAs with the previously isolated [Asp49]PLA2 cDNA revealed some interesting findings from the viewpoint of evolution. First, the homologies of the 5' and 3' untranslated regions (98% and 89%, respectively) were much higher than that of the protein-coding regions (67%). The predicted secondary structure showed the characteristic stem-loop structures for both the untranslated regions of the mRNAs, suggesting that these regions play some functional role(s) in translation or stability of mRNAs. Second, base substitutions appeared to have occurred at similar rates for the three positions of codons among these PLA2s. The results are discussed in terms of evolution of PLA2s. Northern blot analysis showed that these PLA2s are specific to venom gland.

Resonance Raman study on the active-site structure of a cooperative hemerythrin

Resonance Raman spectra were observed for the oxy and azidomet forms of a cooperative hemerythrin (Hr) isolated from Lingula unguis and a noncooperative Hr from Siphonosoma cumanense. The O-O stretching frequency of the oxy derivative of the L. unguis Hr was lower in the high-affinity form generated at pH 7.6 than in the low-affinity form generated at pH 6.2, while that of the S. cumanense Hr did not change at those two pH values. The Fe-O-Fe symmetric stretching mode of L. unguis azidomet-Hr exhibited a frequency shift between pH 7.6 and 6.2, while that of S. cumanense was not shifted. However, the corresponding band of the oxy form did not show a pH-dependent frequency change. Therefore, it is noted that the azidomet form is not a suitable model for studying a mechanism of cooperativity, contrary to the structural similarity between the oxy and azidomet forms. The Fe-O2 as well as Fe-N3 stretching frequencies were found to have no relation with the oxygen affinity. Upon exchange of solvent from H2O to D2O, the O-O and Fe-O2 stretching modes of L. unguis Hr were shifted to higher and lower frequencies, respectively, and their magnitudes were the same for the high- and low-affinity forms. The same frequency shifts were observed for S. cumanense Hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Kinetics of the reconstitution of hemoglobin from semihemoglobins alpha and beta with heme

Kinetics of the reconstitution of hemoglobin from semihemoglobins alpha and beta with hemin dicyanide have been investigated using three kinds of stopped-flow technique (Soret absorption, fluorescence quenching of tryptophan, and Soret CD). The semihemoglobins alpha and beta are occupied by heme in the alpha and beta chains, respectively, the other chain being heme-free. Based on the kinetic results, the following scheme for the reconstitution is proposed; First, hemin dicyanide enters the pocket-like site of the apo chains. Second, in semihemoglobin alpha, the CN-ligand in the fifth coordination position of iron is replaced by the imidazole ring of the proximal His immediately after the heme insertion. In contrast, semihemoglobin beta changes its conformation after the heme insertion, and this is followed by the ligand replacement. Finally, the partial structure changes induced by the ligand replacement propagate onto the whole molecule and the final conformation is attained. The results indicate that semihemoglobin alpha retains a more rigid and organized structure, and more closely approaches its final structure than does semihemoglobin beta.

Analysis of borderline-resistant strains of methicillin-resistant Staphylococcus aureus using polymerase chain reaction

Identification of methicillin-resistant Staphylococcus aureus by drug-susceptibility tests alone poses a serious problem, because a considerable number of clinical S. aureus isolates are borderline resistant to methicillin. To circumvent this problem, we have developed a quick and sensitive method of PCR amplification for the detection of mecA gene, which, coding for PBP2', is the specific genetic element of methicillin-resistant Staphylococcus aureus. This method made it possible to identify MRSA strains in a short time using as few as 30 cells as a starting material for template DNA. Using this method, we found that the strains of borderline methicillin-resistance could be accurately identified. We also found one S. aureus clinical strain, T3, which lacked mecA gene in spite of its resistance to methicillin.

[Graduated psychosomatic treatment and quality of life in asthmatics]

We investigated the quality of life (QOL) in 72 patients with bronchial asthma who are under our gradational psychosomatic treatment (GPT) by means of an 11-item questionnaire. The results were summarized as follows: 1) Ninety-two percent of the subjects showed a good understanding of mind-body relations and modified their stressful adaptive patterns. 2) Asthmatic symptoms improved in 86 percent of the subjects. Other symptoms also improved in 72 percent of the subjects. 3) In 81 percent of the subjects, their daily life improved. Furthermore 96 percent of the subjects obtained some advantages through GPT. 4) There were various improvements in psychological states, personal relations and life style in most of the subjects. 5) The attitudes of their families toward the patients improved in 46 percent of the subjects, however 71 percent of the families developed a better understanding of the cause of asthma from the psychosomatic point of view. 6) Most of the subjects with moderate or severe symptoms were considered to have reduced the grade of severity of their symptoms from the doctor's standpoint.

[Anatomical study of the normal and degenerative articular surfaces on the first carpometacarpal joint]

Specimens of 138 first carpometacarpal joints (CMJ) from cadavers consisting of 59 females and 79 males and averaging 68.8 years of age were grossly evaluated and morphological measurements were performed. Macroscopic degeneration of cartilage surface was noted in the metacarpus of 97 hands and trapezium of 73 hands. 1) Morphological measurements of normal articular surfaces showed that metacarpal concave depth was shallower in the female than in the male and trapezial convex height was flatter in the female than in the male. 2) The degeneration of the articular surface was more often observed in the metacarpal joint than the trapezial joint, and the degree of degenerative changes on each articular surface was greater in the female than in the male. 3) In Grade I, the degeneration of the cartilage surface was observed both in the radial and ulnar facets of the trapezium and in the dorsal and palmar facets of the metacarpus. 4) As the degeneration progressed in both sexes, the trapezial concavity became deeper and its convexity became flatter than normal. On the other hand, the metacarpal concavity was flatter and its convexity was higher than normal. Moreover, these changes were more apparent in the female than in the male.

[Psychosomatic study of inhalation therapy in patients with bronchial asthma. II. Relationship between subjective self assessment of dyspnea and peak expiratory flow rates]

The degree of dyspnea when using metered-dose inhalers (MDIs), and the relationship between subjective self assessments and objective peak expiratory flow rates were examined by means of visual analogue scales and mini wright peak flow meters in 16 subjects with asthma. Three subjects who were neurotic in character were found to have a poor perception of the degree of airway obstruction after inhalation compared with objective changes in their condition. Two subjects, one neurotic and one alexithymic, assessed the degree of dyspnea to be worse after inhalation, when objectively there were few changes. However, one neurotic subject perceived an improvement in his condition when, in fact, there was little change. Furthermore, some severe cases used MDIs in the rogressive state of airway obstruction. In conclusion, we must pay attention to patients' characters when determining treatment in order to prevent overuse of MDIs or delays in treatments including the use of MDIs.

[Psychosomatic study of inhalation therapy in patients with bronchial asthma. I. Evaluation by questionnaire]

We investigated the use of metered-dose beta agonist inhalers (MDIs) by means of 17-item questionnaires from the standpoint of psychosomatic medicine in 56 subjects with bronchial asthma. The results can be summarized as follows: 1) Many asthmatics with neurotic characters used MDIs frequently; Thirteen percent of them suffered adverse effects. The number of times the inhalers were used increased in proportion to the severity and the duration of illness. Fifteen percent of the subjects used MDIs frequently because of anxiety. 2) Fifty percent of the subjects, most of them had neurotic or alexithymic characters, used MDIs without suffering from dyspnea or wheezes; the subjects who used MDIs because of anxiety increased in proportion to the duration of illness. 3) Seventy eight percent of the subjects were anxious about asthmatic attack when they did not carry any MDI; sixty two percent of the subjects, most of them had neurotic or alexithymic characters, actually experienced asthmatic attack. 4) Seventy three percent of the subjects used MDIs secretly; sixty percent of the subjects did not like to inhale in the presence of others. 5) There were some subjects who acted incorrectly on or after asthmatic attack when MDIs were not effective.

Changes in T-cell subpopulations induced by autonomic neurotransmitters and hormone

In our previous studies, we found that changes in T-cell subpopulations were induced by restraint stress. To determine how this influence on the immune system was mediated pharmacologically, we studied the effects of autonomic agonists and antagonists and hydrocortisone on T-cell subpopulations in C3/H mice. These agents induced changes in the subpopulations of T-cells and modulated the receptors on T-cells. These drugs, however, did not have the same effect as restraint stress. This suggests that the effect of restraint stress on the immune system is mediated by other mechanisms. We found autonomic agents and hydrocortisone to affect differently T-cells in various organs. In general, acetylcholine and hydrocortisone affected T-cells in the thymus and adrenaline affected those in the spleen. By the double staining method, the maturity of these T-cells was found to be affected by these drugs. Remarkable changes were as follows. Thy 1, 2-positive T-cells were decreased in the blood and increased in the spleen while Lyt 2-positive T-cells were increased in the spleen by adrenaline. Thy 1, 2-positive T-cells were decreased in the thymus and increased in the blood while L3T4-positive T-cells and Lyt 2-positive T-cells in the blood were increased by acetylcholine. L3T4-positive T-cells were decreased in the thymus by atropine. Finally, Lyt 2-positive T-cells in the thymus were decreased and L3T4-positive T-cells in the blood were increased by hydrocortisone.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of stress on the maturity of T-cells

Stress is known to influence the immune function via an effect on the central nervous system. We previously presented data showing that stress alters the population of T-cell subsets in mice. The variations of T-cell subsets in the thymus, peripheral blood, and spleen in mice similarly stressed by immobilization or by unavoidable and opioid-dependent stress were measured by flow cytometry using the monoclonal antibodies anti-L3T4, anti-Lyt 1, anti-Lyt 2 and anti-Thy 1, 2. Immobilization stress was applied for three days and T-cell subsets were measured on the days 1, 2 and 3, as well as on day 7 after release from immobilization. Lyt 2-positive cells in the thymus were the most sensitive to stress, showing significant variations. The proportion of immature T-cells increased in the thymus, blood and spleen of the stressed mice. When diazepam or naloxone were administered 30 min before the initiation of stress, these variations tended to decrease. Thus, the ratio of T-cell subsets varied with the duration of immobilization stress. This appeared to be partly mediated by the opioid system and the central nervous system.

Amino acid sequence of a phospholipase A2 from the venom of Trimeresurus gramineus (green habu snake)

Two phospholipases A2, named phospholipases A2-I and A2-II, were purified to homogeneity from the venom of Trimeresurus gramineus (green habu snake). The complete amino acid sequence of phospholipase A2-I was determined by sequencing the native protein and the peptides produced by enzymatic (Achromobacter protease I, clostripain, and chymotrypsin) and chemical (hydroxylamine) cleavages of the S-pyridylethylated derivative of the protein. The protein consisted of 122 amino acid residues and was similar in sequence to phospholipases A2 from the venoms of crotalid snakes which belong to the category of Group II. A most striking feature of this protein is that tyrosine at the 28th position which is common in phospholipases A2 and is assumed to be a part of the Ca2(+)-binding loop is replaced by phenylalanine. Such replacement is the first finding in Group II phospholipases A2. Secondary structure compositions of phospholipase A2-I are similar to those of Crotalus atrox phospholipase A2. No appreciable Ca2(+)-induced difference spectrum was observed, due probably to the absence of the effective chromophoric groups in the neighborhood of the Ca2+ binding site although Ca2+ is bound with affinity similar to that for T. flavoviridis phospholipase A2.

Cloning and sequence analysis of cDNA for Trimeresurus flavoviridis phospholipase A2, and consequent revision of the amino acid sequence

A cDNA clone of Trimeresurus flavoviridis phospholipase A2 was isolated from the venom gland cDNA library using DNA amplified by polymerase chain reaction with oligonucleotide primers corresponding to the N- and C-terminal sequences of this enzyme. The amino acid sequence deduced from the cDNA nucleotide sequence determined by the dideoxy termination method was found to be inconsistent in the segment comprising the 69th to 81st positions from that reported previously [Tanaka, S. et al. (1986) J. Biochem. 99, 281-289]. Reinvestigation of the amino acid sequence of the peptide covering the sequence in question showed that the amino acid sequence predicted from the nucleotide sequence is correct. The sequence contains Asn-Asn-Gly (positions 69-71) and it was found that the Asn-Gly bond easily undergoes alpha-beta transpeptidation when digested with Achromobacter protease I at pH 9.0 but not seriously at pH 6.8. It is likely that the transpeptidation reaction caused a failure in the previous sequence determination. The cDNA clone obtained was 597 base pairs long and contained an open reading frame of 414 base pairs coding for 138 amino acid residues. A typical signal peptide sequence (16 amino acid residues long), located at the N-terminal moiety of the deduced sequence, was immediately followed by a polypeptide which corresponds to the mature enzyme. Northern blot analysis showed a single transcript only in the poly(A)+ RNA fraction of the venom gland but not in those of many other organs tested.

Purification and characterization of a coagulant enzyme, okinaxobin I, from the venom of Trimeresurus okinavensis (Himehabu snake) which releases fibrinopeptide B

A coagulant enzyme, named okinaxobin I, has been purified to homogeneity from the venom of Trimeresurus okinavensis (Himehabu) by chromatographies on Sephadex G-100 and CM-Toyopearl 650M columns. The enzyme was a monomer with a molecular weight of 37,000 and its isoelectric point was 5.4. The enzyme acted on fibrinogen to form fibrin clots with a specific activity of 77 NIH units/mg. Fibrinopeptide B was released at a rate much faster than fibrinopeptide A. The enzyme exhibited 2 to 3 times higher activity toward tosyl-L-arginine methyl ester and benzoyl-L-arginine p-nitroanilide than bovine thrombin. The esterase activity was strongly inhibited by diisopropylfluorophosphate and phenylmethanesulfonyl fluoride, and to a lesser extent by tosyl-L-lysine chloromethyl ketone, indicating that the enzyme is a serine protease like thrombin. The N-terminal sequence was highly homologous to those of coagulant enzymes from T. flavoviridis and Bothrops atrox, moojeni venoms which preferentially release fibrinopeptide A. In order to remove most, if not all, of the bonded carbohydrates, the enzyme was treated with anhydrous hydrogen fluoride (HF), thereby reducing the molecular weight to 30,000. The protein contained approximately 260 amino acid residues when computation was based on this value. The HF-treated enzyme retained about 50% of the clotting and esterolytic (TAME) activities and preferentially released fibrinopeptide B from fibrinogen. The carbohydrate moiety is not crucial for enzyme activity but might be necessary for eliciting full activity.

[Pulmonary infiltration with eosinophilia possibly induced by cefotiam in a case of steroid-dependent asthma]

A 37-year-old female with refractory asthma taking betamethasone orally (1 mg/d), showed a fever of 38.5 degrees C, productive cough and dyspnea. The chest X-ray demonstrated diffuse infiltration in the left lower lung field. The WBC count was 16,000/mm3 with 6% eosinophils. She was treated with intravenous drip infusion of antibiotics (Cefotiam 2 mg/d and Sisomicin 150 mg/d) for 2 weeks, and her symptoms and the chest X-ray findings improved. However, at the end of the therapy eosinophilia was noticed. Sixteen days after the completion of antibiotic therapy, she again experienced fever, cough and dyspnea. The chest X-ray again demonstrated diffuse infiltrations in the left lower lung field. The total IgE level, histamine and circulating immune complex titers were elevated. The WBC count was 14,700/mm3 with 34% eosinophils. Although a sputum culture yielded no organisms, many eosinophils were observed in the sputum. There were no clinical or laboratory findings compatible with allergic broncho-pulmonary aspergillosis. After the administration of oral prednisolone (40 mg/d), the patient showed rapid improvement with resolution of all symptoms and normalization of the IgE, histamine and circulating immune complex levels. The chest X-ray revealed marked regression of the pulmonary infiltrations. A microscopic examination of a transbronchial biopsy specimen demonstrated moderate eosinophilic infiltrations. It was compatible with the diagnosis of pulmonary infiltration with eosinophilia. Treatment was performed with prednisolone. The result of a lymphocyte stimulation test was positive for Cefotiam. An in vitro test was performed to evaluate the diagnosis of drug allergy in this case.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissociation of Limulus polyphemus (horseshoe crab) hemocyanin

A solution X-ray scattering study has been performed on Limulus polyphemus (horseshoe crab) hemocyanin and its dissociated fragments at various pH values in the presence and absence of Ca2+. The scattering patterns of native hemocyanin (48-mer), the half molecule (24-mer), quarter molecule (12-mer) and monomer fraction were measured. The radii of gyration for the four molecular species were calculated from the Guinier plots to be 110.7, 91.3, 77.3, and 36.5 A, respectively. Models which yield good fits to the experimental data are presented. The models were constructed using eight, four and two spheres with a radius of 58 A, assuming the sphere to be the submultiple composed of six subunits. The radii of gyration were calculated on the basis of the model and the values found to be 106, 94 and 73 A, respectively, in good agreement with the experimental results.

Effective therapy with low dose of oral cyclosporine A and prednisolone for alopecia universalis

Although alopecia universalis is an incurable disease, we have obtained favorable results using a low dose of 2.5 mg/kg of cyclosporine A and 5 mg/day of prednisolone without adverse effects. We report our clinical experience of the treatment of two cases of alopecia universalis. Immunological examinations showed marked changes in the ratio of T cell subsets in peripheral blood. There was an increase of OKT8 positive cells and NK cells, reduction of IL-2R positive cells. These immunological changes following recovery from alopecia suggest a correlation between immunological disorders and the pathogenesis of this disease (alopecia universalis).

Structural kinetics of the allosteric transition of aspartate transcarbamylase produced by physiological substrates

We have studied the kinetics of the quaternary structure change associated with the allosteric transition of aspartate transcarbamylase (ATCase) (E. coli), inducing this change by exposure to the natural substrates (carbamyl phosphate and L-aspartate). The presence of 30% ethylene glycol slowed the quaternary structure change sufficiently for it to be followed by stopped-flow X-ray scattering at -5 degrees C. After adding substrates to the enzyme, the change occurred, with a half-life of a few seconds, yielding a mixture of the two standard quaternary structures (or, conceivably, a state intermediate between them). This mixture persisted until the enzyme reduced the substrate concentration below a threshold value.

Hemerythrin from Lingula unguis consists of two different subunits, alpha and beta

Hemerythrin, a non-heme Fe-protein, of Lingula unguis has an octamer structure. We demonstrated that the protein is composed of two distinct subunits (alpha and beta), in equal amounts by investigation of their composition and partial terminal sequence. The cross-linking reaction of the native protein with dithiobis-(succinimidyl propionate) provided evidence for the presence of a dimer composed of alpha and beta subunits.

Purification and amino acid sequence of basic protein II, a lysine-49-phospholipase A2 with low activity, from Trimeresurus flavoviridis venom

A basic protein (pI 10.3), named basic protein II, was purified to homogeneity from the venom of Trimeresurus flavoviridis (Habu snake) after four chromatographic steps. The amino acid sequence of this protein was determined by sequencing the S-pyridylethylated derivative and its peptides produced by chemical (cyanogen bromide) and enzymatic (chymotrypsin, clostripain, and Staphylococcus aureus V8 protease) cleavages. The protein consisted of 122 amino acid residues and was found to be identical in sequence to basic protein I from the same source except that Asp-58 of basic protein I is replaced by asparagine. Like basic protein I, the structural feature of basic protein II is that Tyr-28 and Asp-49 common in phospholipases A2 from snake venoms and mammalian pancreas are replaced by asparagine and lysine, respectively. Thus, basic protein II belongs to the category of lysine-49-phospholipase A2. The action of basic protein II on 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphorylcholine released only oleic acid, indicating that it has phospholipase A2 activity. Its molar activity toward 1,2-dilauroyl-sn-glycero-3-phosphorylcholine, however, was only 1.7% of that of T. flavoviridis phospholipase A2 isolated previously. Affinity for Ca2+ and reactivity toward p-bromophenacyl bromide of basic protein II were 8 and 5.3 times, respectively, smaller than those of phospholipase A2 from the same source, substantiating the low phospholipase A2 activity of basic protein II.

Binding of Cu(II), Tb(III) and Fe(III) to chicken ovotransferrin. A kinetic study

The kinetics of binding of Cu(II), Tb(III) and Fe(III) to ovotransferrin have been investigated using the stopped-flow technique. Rate constants for the second-order reaction, k+, were determined by monitoring the absorbance change upon formation of the metal-transferrin complex in time range of milliseconds to seconds. The N and C sites appeared to bind a particular metal ion with the same rate; thus, average formation rate constants k+ (average) were 2.4 x 10(4) M-1 s-1 and 8.3 x 10(4) M-1 s-1 for Cu(II) and Tb(III) respectively. Site preference (N site for Cu(II) and C site for Tb(III] is then mainly due to the difference in dissociation rate constant for the metals. Fe(III) binding from Fe-nitrilotriacetate complex to apo-ovotransferrin was found to be more rapid, giving an average formation rate constant k+ (average) of 5 x 10(5) M-1 s-1, which was followed by a slow increase in absorbance at 465 nm. This slow process has an apparent rate constant in the range 3 s-1 to 0.5 s-1, depending upon the degree of Fe(III) saturation. The variation in the rate of the second phase is thought to reflect the difference in the rate of a conformational change for monoferric and diferric ovotransferrins. Monoferric ovotransferrin changes its conformation more rapidly (3.4 s-1) than diferric ovotransferrin (0.52 s-1). A further absorbance decrease was observed over a period of several minutes; this could be assigned to release of NTA from the complex, as suggested by Honda et al. (1980).

Purification and amino acid sequence of basic protein I, a lysine-49-phospholipase A2 with low activity, from the venom of Trimeresurus flavoviridis (Habu snake)

A basic protein (pI 10.2), named basic protein I, was purified to homogeneity from the venom of Trimeresurus flavoviridis (Habu snake) after four chromatographic steps. The amino acid sequence of this protein was determined by sequencing the S-pyridylethylated derivative of the protein and its peptides produced by chemical (cyanogen bromide and formic acid) and enzymatic (chymotrypsin, Achromobacter protease I, and Staphylococcus aureus V8 protease) cleavages. The protein consisted of 122 amino acid residues and was similar in sequence to phospholipases A2 from the venoms of crotalid and viperid snakes. A most striking feature of this protein is that aspartic acid at the 49th position common in phospholipases A2 is replaced by lysine. When the protein acted on 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphorylcholine, oleic acid was preferentially released, indicating that the protein has phospholipase A2 activity. Its molar activity toward 1,2-dilauroyl-sn-glycero-3-phosphorylcholine, however, was 1.5% that of T. flavoviridis phospholipase A2 isolated previously. The fact that both affinity to Ca2+ and reactivity to p-bromophenacyl bromide of basic protein I are approximately one order of magnitude lower than those of T. flavoviridis phospholipase A2 might explain the low activity of basic protein I.

Preliminary crystallographic study of phospholipase A2 from the venom of Trimeresurus flavoviridis (habu snake)

Crystallization and a preliminary crystallographic study of Trimeresurus flavoviridis (habu snake) phospholipase A2 (PLA2) were carried out. Although crystals were obtained from various solutions, crystals suitable for X-ray analysis could be obtained from polyethylene glycol solutions only when a repeated seeding technique was applied starting from twinned crystals. The crystal is monoclinic with space group P21, with a = 44.1, b = 55.7, c = 48.8 A, and beta = 92.4 degrees. An asymmetric unit contains a dimer consisting of two identical subunits made of 122 amino acids. The crystal reflects X-rays beyond 2.5 A. A Pt derivative gave a good isomorphous crystal.

Prevention of immunosuppression in stressed mice by neurotropin(NSP)

It is well known that the immune function can be compromised by stress. To investigate immune function in mice stressed by experimental restraint or unavoidable and opioid dependent stress, we evaluated the changes in total body weight and in organ weights (liver, spleen and thymus) of these animals, as well as the phagocytic activity of macrophages, the cytotoxicity of T cells and inhibitory effects on tumor growth and changes in T cell subset populations. At the same time we evaluated the effects of Neurotropin (NSP), a substance extracted from the inflamed skin of rabbits inoculated with the vaccinia virus and which appears to possess neuroimmunomodulating activity. The experimentally stressed group exhibited a reduction of phagocytic activity of macrophages, cytotoxicity of T cells and inhibitory effects on tumor growth. In addition there were changes in the population of T cell subsets. In those animals pretreated with NSP, the immunosuppression induced by stress was ameliorated. As compared with several agents which influence phagocytosis, neurotropin exhibited effects similar to that of agents that blocked the adrenaline receptor and an opioid antagonist rather than tranquilizer (diazepam) and a cholinergic receptor blocker. The pharmacologic effects of neurotropin support a relationship between the actions of the central nervous system and the immune system.

Investigation of an active site histidine-aspartate couple in Trimeresurus flavoviridis phospholipase A2

When Trimeresurus flavoviridis phospholipase A2 was reacted with methyl p-nitrobenzenesulfonate, its activity decreased following first-order kinetics. The pH dependence of the rate constants of inactivation showed that His-48 with an apparent pKa of 6.5 controls the reaction. In the pH region below 6.5, N1-methylhistidine was predominantly formed. On the other hand, N1,N3-dimethylhistidine was almost exclusively produced in the pH region above 6.5. No N3-methylhistidine was detected at any pH tested. Such observations suggested that the first methylation occurred at the N1-position of the imidazole ring followed by a second methylation at the N3-position, and that His-48 couples the carboxylate of Asp-99 at the N3-position of the imidazole ring, in accord with the interaction observed in the crystal structure of homologous Crotalus atrox phospholipase A2. As it has been reported that, in the reaction of chymotrypsin with methyl p-nitrobenzenesulfonate at pH 7.8, only monomethylation occurred at the N1-position of the His-57 imidazole group (Nakagawa, Y. & Bender, M.L. (1970) Biochemistry 9, 259-267), the nature of the active site histidine-aspartate couple of T. flavoviridis phospholipase A2 seems not to be identical with that of chymotrypsin.

A monoclonal antibody that triggers deacylation of an intermediate thrombin-antithrombin III complex

Upon incubation of antithrombin III with thrombin in the presence of a monoclonal antibody recognizing an epitope exposed on the heavy chain part of thrombin-cleaved two-chain antithrombin III, antithrombin III was preferentially cleaved by the enzyme as a substrate, rather than covalently complexed with the enzyme to form an equimolar, stable acyl complex. Once the stable acyl complex was formed between the enzyme and antithrombin III, however, no further liberation of two-chain antithrombin III was observed. Kinetic studies showed that heparin does not affect this reaction, although generation of thrombin-cleaved two-chain antithrombin III is apparently accelerated in accordance with the rate constant for heparin-enhanced thrombin-antithrombin III complex formation. Here we propose the term "switching antibody" for an antibody that triggers deacylation of an intermediate enzyme-inhibitor complex by switching the enzyme-inhibitor reaction from the major pathway of stable acyl complex formation to an alternative pathway of cleavage of the inhibitor as a substrate.

Negative cooperativity of chicken ovotransferrin on Al(III)-binding

Chicken ovotransferrin, an iron binding protein, has two metal binding sites (amino (N) and carboxy (C) terminal sites). It binds Cu(II), Al(III), Co(II), and other metals, as well as Fe(III). In this study, the selectivity and cooperativity of the N and C sites on Al(III), Co(II), and Tb(III) binding were investigated. Metals were classified into two groups according to their site preference. Co(II) and Al(III) bound to the N site more preferably than to the C site, whereas Tb(III) bound to the C site more preferably. On Fe(III) binding, the binding constant of Fe(III) becomes larger when the other site is already occupied. Thus, positive cooperativity is seen. In the present study, the binding cooperativities of Co(II), Tb(III), and Al(III) as to the N and C sites were investigated. On Co(II) and Tb(III) binding, no cooperativity was observed, as in the case of Cu(II) [Yamamura, T. et al. (1985) in Proteins of Iron Storage and Transport (Spik, G., Montreuil, J., Crichton, R.R., & Mazurier, J., eds.) pp. 53-56, Elsevier Science Publ. B.V., Amsterdam]. In contrast, negative cooperativity was observed on Al(III) binding. Based on a model proposed by Yamamura et al. [Yamamura, T. et al. (1985) ibid.], the ratio of the binding constants, KC/KN, and the stacking coefficient, Kst, were estimated. KC/KN is 2.2 +/- 0.4 for the Tb(III) ion, 0.5 +/- 0.1 for the Co(II) ion, and 0.12 +/- 0.02 for the Al(III) ion. Kst (= 1 in a non-cooperative case) is 0.98 +/- 0.02 for the Tb(III) ion, 1.03 +/- 0.02 for the Co(II) ion, and 0.55 +/- 0.22 for the Al(III) ion.

Kinetic study on the dimer-tetramer interconversion of phosphorylase b by a stopped-flow X-ray scattering method

The dimer-tetramer interconversion of phosphorylase b induced by the binding of AMP and Mg2+ was monitored using a stopped-flow X-ray scattering method. The rate constants of this second-order reaction have been determined by a nonlinear least-squares method. Burst phases in both radii of gyration and zero-angle intensities were detected at the initial step of the reaction. This suggests that rapid association might take place, followed by a slow association process of which the kinetics were measured in the present study. The radius of gyration of tetrameric phosphorylase b was determined and found to be in excellent agreement with that of phosphorylase a, but different from that of phosphorylase b reported elsewhere (G. Puchwein, O. Kratky, C. F. Golker and E. Helmreich, Biochemistry 9 (1970) 4691). The reason for this inconsistency is discussed.

Auto-oxidation of Lingula unguis and Siphonosoma cumanense hemerythrins induced by some perturbants

Auto-oxidation of human adult hemoglobin and Siphonosoma cumanense and Lingula unguis hemerythrins were investigated in the presence and absence of perturbants. In the presence of urea, there were no drastic increases in auto-oxidation rates for the three proteins. In contrast, thiocyanate and laurate enhanced the auto-oxidation rates remarkably. In the presence of thiol reagents such as PCMB and NEM, auto-oxidation rates were enhanced with dissociation into subunit, but not enhanced so much with SH-modification only. Thus oligomerization is probably necessary to protect auto-oxidation.

Dissociation and auto-oxidation of hemerythrin induced by SH-modification: a kinetic study

Hemerythrin from Siphonosoma cumanense has a trimeric structure consisting of identical subunits, which have no cooperativity nor Bohr effect on oxygen-binding. The trimer was dissociated into its monomers by the modification of the SH group of its cysteines with p-chloromercuriphenylsulfonic acid (PCMPS), which was monitored by stopped-flow of both spectrophotomeric and small angle X-ray scattering methods. The results showed that the process involved sequential modification of the SH groups, dissociation into monomers, and auto-oxidation of ferrous iron in the active center. The modification of the SH groups with PCMPS followed second-order kinetics with a rate constant of 1.8 M-1.s-1. The dissociation and auto-oxidation followed first-order kinetics with rate constants of 4 X 10(-3) s-1 and 5 X 10(-4) s-1, respectively. The obtained rate of auto-oxidation was much faster than that in the native state. These findings lead to the conclusion that the trimeric state of S. cumanense hemerythrin is necessary to prevent auto-oxidation.

Transition of environmental polarity of tyrosine-76 of Trimeresurus flavoviridis phospholipase A2 upon active site ligand binding

Modification of Trimeresurus flavoviridis phospholipase A2 with a 5-fold molar excess of tetranitromethane produced 40% active mononitrotyrosyl phospholipase A2 in which Tyr-76 was specifically nitrated. This is in contrast to the case of mammalian pancreatic phospholipases A2 where Tyr-70 but not Tyr-76 was nitrated. When Ca2+ was bound to T. flavoviridis mononitrotyrosyl phospholipase A2, nitrated tyrosine (Tyr(NO2))-76 moved from a less polar site to a polar site with the decrease of the pKa value of its hydroxyl group. Nitration of Tyr-76 did not influence the binding affinity to Ca2+. Addition of laurylphosphorylcholine to mononitrotyrosyl phospholipase A2 in the presence of Ca2+ caused the movement of Tyr(NO2)-76 from a polar environment to a less polar environment with the rise in the pKa value. Tyrosine-76 is located in the site whose environmental polarity is affected by the binding of the ligands to the active site. As Tyr-76 is located in the site not proximal to the active site, it could be assumed that the conformational change induced by the binding of the ligands extends to the region remote from the active site in T. flavoviridis phospholipase A2. This might provide evidence of long-range diffusional coupling between remote sites in the noncooperative globular protein.

Amino acid sequence of a coagulant enzyme, flavoxobin, from Trimeresurus flavoviridis venom

The amino acid sequence of a coagulant enzyme, named flavoxobin, isolated from the venom of Trimeresurus flavoviridis (the habu snake) was determined by sequencing the S-pyridylethylated derivative of the protein and its peptides generated by chemical (cyanogen bromide and hydroxylamine) and enzymatic (clostripain, Staphylococcus aureus V8 protease, Achromobacter protease I, and elastase) cleavages. Hydrazinolysis was also employed to determine the C-terminal amino acid. The enzyme consisted of 236 amino acids and had a calculated molecular weight of 25,744. Flavoxobin was found to be highly (69%) homologous in sequence to batroxobin, a coagulant enzyme from the venom of Bothrops atrox, and 27, 39, and 31% homologous to bovine thrombin, bovine trypsin, and human kallikrein, respectively. The sequence around the active site serine residue deduced from the homology relationship was Phe-Asp-Ser-Gly-Thr, which is different from the common sequence, Gly-Asp-Ser-Gly-Gly, for most serine proteases. Flavoxobin appears to be similar in secondary structure composition to batroxobin.

Proton NMR resonance assignments and surface accessibility of tryptophan residues of a dimeric phospholipase A2 from Trimeresurus flavoviridis

Proton NMR spectra of a dimeric phospholipase A2 from Trimeresurus flavoviridis have been recorded. N-1 proton resonances of the tryptophan indole rings have been detected and assigned to specific positions, Trp-3/Trp-30, Trp-68 and Trp-108, by comparing the spectra of the enzyme derivatives with tryptophans oxidized to differing extents. Photo-CIDNP experiments have revealed that Trp-68 and Trp-108 are exposed while Trp-3 and Trp-30 are buried in the molecule. This is consistent with the X-ray crystal structure of a homologous phospholipase A2 from Crotalus atrox where residues 3 and 30 are located at a dimer interface, but inconsistent with the results of stepwise oxidation of tryptophan residues.

Reconstitution of myoglobin from apoprotein and heme, monitored by stopped-flow absorption, fluorescence and circular dichroism

The reconstitution reaction of ferric cyanomyoglobin from apomyoglobin and hemin dicyanide was investigated with a stopped-flow apparatus by the use of five kinds of probes; (a) Soret absorption, (b) fluorescence quenching of tryptophan, (c) far-ultraviolet CD, (d) near-ultraviolet CD, and (e) Soret CD. After mixing of apomyoglobulin with equimolar amounts of hemin dicyanide, the Soret absorption band was shifted to longer wavelengths within 10 ms. The shifted band kept its shape for a few seconds, and then gradually shifted to shorter wavelengths. A rate constant of the slow reaction was 1.1 x 10(-2) s-1. Time courses of fluorescence quenching followed a second-order reaction with a rate constant of 9 x 10(7) M-1 s-1. Far-ultraviolet CD recovered to the level of native state within the response time of an apparatus (= 64 ms). Near-ultraviolet CD and Soret CD changed with first-order rate constants of 5-30 s-1 and 5 x 10(-3) s-1 respectively. On the basis of the kinetic results we propose the following reconstitution pathway of myoglobin. Apomyoglobin has essentially a highly folded structure similar to myoglobin, but there are some differences in the secondary structure between them. In the first step, heme enters the pocket-like site of apomyoglobin and interacts with surrounding hydrophobic residues in the pocket, and then the interaction may give a complete ordered structure to the protein. Second, the tertiary structure of the heme pocket is partly constructed. Third, the iron-proximal His bond occurs, followed by the attainment of the final conformation. This sequence of the events shows that the polypeptide chain is entirely folded before the completion of three-dimensional structure of the heme pocket. The reconstitution pathway is fairly different from that of the alpha subunit of hemoglobin reported by Leutzinger and Beychok [Proc. Natl Acad. Sci. USA (1981) 78, 780-784], which described how a drastic recovery in helicity was observed on the heme-binding, and that the recovery is introduced by the formation of the heme pocket structure. The difference in the results found for the alpha subunit and myoglobin suggests a difference in conformation: in apomyoglobin most of the helices are arranged and folded around a helix core to form a compact structure as a whole, while in apo-alpha subunit some helices are not folded around the helix core. Helix D, which is absent in the alpha subunit, may play an important role in folding of the helices.

Tryptophan residue essential for activity of Naja naja atra phospholipase A2

When Naja naja atra phospholipase A2, which contains three tryptophan residues at the 18th, 19th, and 61st positions, was oxidized with N-bromosuccinimide at pH 4.0, its activity decreased in a convex manner with increase in the extent of oxidation of tryptophan residues. The curve shape showed that the tryptophan residue oxidized last is most responsible for the activity. The order of accessibilities of the three tryptophan residues, which was analyzed according to the method reported previously (Mohri et al. (1876) J. Biochem. 100, 883-893), was Trp-61 greater than Trp-19 greater than Trp-18. Thus, Trp-18 was evaluated to be essential for activity. Difference spectra of phospholipase A2 produced by titrating with laurylphosphorylcholine in the presence of Ca2+, which are due in large part to perturbation of the tryptophan residue(s), were retained with phospholipase A2 derivatives containing 1.2 and 2.0 mol of tryptophan residues oxidized but not with the derivative containing 3.0 mol of tryptophan residues oxidized. Such observations led us to assume that Trp-18 is involved in the specific site that interacts with phospholipid.

Tetrodotoxin-unaffected depolarization of frog muscles induced by the venom of jellyfish (Genus aurelia)

In the isolated frog muscle, the proteinaceous venom extracted from jellyfish (genus Aurelia) produced 1) a complete and irreversible block of indirectly and directly elicited muscle twitch and 2) an irreversible depolarization of the muscle membrane. This venom-induced depolarization was effectively reversed or prevented by the substitution of choline for sodium in Ringer solution, but not by the introduction of tetrodotoxin (TTX), a sodium channel blocker. The mechanism of muscle membrane depolarization appears to involve probably an increase in membrane permeability to sodium ion as shown by the decrease in membrane resistance. These results suggest that the venom forms a pore which has sodium selectivity or activates a TTX-insensitive sodium channel which is different from the known sodium channel.

Kinetics of structure and activity changes during the allosteric transition of aspartate transcarbamylase

For the first time, the structural change associated with an allosteric transition has been monitored by X-ray solution scattering. The kinetics of the quaternary structure change of aspartate transcarbamylase were first slowed by using acetyl phosphate instead of carbamyl phosphate, and by the presence of 10% or 30% ethylene glycol. At 6.5 degrees C, the quaternary structure change was found to have a time constant of about 11 seconds. This appears to be larger than that obtained for the switching of homotropic co-operativity, measured by chemical quench under the same conditions.