[Clinical evaluation of myasthenia gravis in elderly patients]

In Japan, elderly patients who develop myasthenia gravis (MG) are increasing in number. However, there are few clinical reports concerning this issue. We evaluated the clinical manifestations, inducing or exacerbating factors, complications, treatments and prognosis of systemic MG in 11 patients older than 60 years of age. Bulbar symptoms were more frequent in these patients compared with younger MG patients, and 6 out of 11 cases (54.5%) were mistakenly diagnosed as cerebrovascular disorders. Among inducing or exacerbating factors of MG were psychological problems inherently involved with the aged, physical factors, and inappropriate termination or rejection of medication. Increase in the level of anti-Ach-R antibodies was recognized in 10 out of 11 cases (90.9%). A high percentage of the patients had thymoma (36.4%) and thyroid diseases (45.5%): 3 with Hashimoto's thyroiditis (27.3%), 1 with thyroid ophthalmopathy associated with hyperthyroidism, and 1 with simple goiter. Others were accompanied by ischemic heart disease, prostatic hypertrophy or stomach cancer. We treated these patients with corticosteroids, immunoglobulin, radiation for thymoma, or thymectomy in addition to administration of anticholinesterase agents. Prognostically, we found that duration of illness before death was shorter in those with onset later than 70 years of age. Seven out of 11 (63.6%) patients died of either aspiration pneumonia (4 cases), complications of thymectomy, congestive pulmonary edema or stomach cancer. There were no deaths associated with myasthenic crisis.

Cloning, sequencing, and expression in Escherichia coli of cDNA encoding porcine brain UMP-CMP kinase

A cDNA encoding porcine brain UMP-CMP kinase has been isolated using two oligonucleotide probes synthesized on the basis of the partial amino acid sequences of the purified enzyme. The isolated cDNA consisted of 1,626 nucleotides including the coding region for a polypeptide of 196 amino acid residues with a calculated molecular weight of 22,279. The enzyme showed an overall sequence identity of about 40 and 50%, respectively, with adenylate kinases from mammalian muscle and Escherichia coli and UMP-CMP kinases from Saccharomyces cerevisiae and Dictyostelium discoideum. The two highly conserved residues, Thr-39 and Leu-66, in adenylate kinases, which are located close to the adenine ring of the bound AMP, are replaced by Ala and Ile, respectively, at the corresponding positions in UMP-CMP kinases. The entire structural gene was inserted 3'-downstream of the strong promoter in the expression plasmid pET-3b. E. coli BL21(DE3) cells carrying the resultant plasmid produced the active enzyme in a soluble state, most efficiently upon induction at 37 degrees C with 0.02 mM isopropyl-beta-D-thiogalactoside. The purified recombinant enzyme catalyzed specific phosphoryl transfer from ATP to UMP and CMP.

Spectroscopic studies on the mechanism of the topa quinone generation in bacterial monoamine oxidase

Electron paramagnetic resonance (EPR), circular dichroism (CD), and optical absorption spectroscopies have been used to investigate the copper-dependent autoxidation process generating the 6-hydroxydopa (topa) quinone cofactor in the recombinant phenethylamine oxidase from Arthrobacter globiformis. The cupric ion bound to the copper/topa quinone-less, inactive enzyme is first reduced to Cu(I), as inferred from the spectroscopic features observed under strictly anaerobic conditions. Cu(I) is also detectable chemically with a Cu(I)-specific chelating agent, bathocuproinedisulfonate. Introduction of a limited amount of oxygen then leads to the formation of a paramagnetic species (g = 2.004) that is stable for over several to 10 min but vanishes swiftly upon addition of sufficient oxygen. Strikingly, the hyperfine EPR structure of the organic radical is almost identical with that of the topa semiquinolamine observed in the copper/topa quinone-containing, active enzyme anaerobically reduced with substrate. Concomitant with the generation of topa quinone exhibiting characteristic optical absorption and CD bands under fully aerobic conditions, the bound copper finally shows EPR signals typical of nonblue type II Cu(II) and optical absorption around 700 nm with negative CD above 700 nm. None of these spectral changes are evoked in the binding of Cu(II) to the Tyr382-->Phe mutant enzyme, indicating that the precursor Tyr382 to topa quinone participates in the initial reduction of bound copper and serves as the origin of the transiently formed semiquinone radical. The prosthetic cupric ion plays an essential role, by changing its redox state, in the oxidative modification of the tyrosyl phenol ring, leading to topa quinone.

A third type of nucleoside diphosphate kinase from spinach leaves: purification, characterization and amino-acid sequence

A third type of nucleoside diphosphate kinase (NDP kinase III), distinct from the previously described NDP kinases I and II (Nomura et al. (1991) Biochim. Biophys. Acta 1077, 47-55), was purified from spinach leaves to electrophoretic homogeneity. NDP kinase III was judged by SDS-PAGE and by gel filtration to have molecular masses of 17 kDa and 102 kDa, respectively, suggesting that it is composed of six subunits similarly to the other spinach isoforms, NDP kinases I and II. Amino-acid sequence analysis revealed the primary structure of NDP kinase III to be comprised of 153 amino-acid residues, the sequence of which exhibited 61% and 53% homology with those of NDP kinases I and II, respectively. In the reaction catalyzed by the three isoforms, the order of Km as phosphate acceptor was determined as GDP << ADP for NDP kinase III, different from those observed for NDP kinase I (ADP << GDP) and for NDP kinase II (GDP = ADP). These results suggest that the three isoforms may have distinct roles in regulating intracellular 5'-di- and 5'-triphosphonucleotide levels in spinach leaves.

[Mirror movements observed in patients skilled in playing the piano--symptomatological study]

We investigated mirror movements observed in two patients skilled in playing the piano and compared these symptoms with those reported in patients associated with frontal lobe, corpus callosum or cervical cord lesion. We found the following common features in our two patients: 1) mirror movements were observed during skilled finger movements such as playing the piano, 2) these were observed in distal parts of the bilateral upper extremities, 3) contralateral imitative associated movements were seen concomitantly, 4) frontal lobe symptoms and callosal disconnection syndrome were not seen, 5) both patients recalled having mirror movements in their infancy, and one had family history. These characteristics of mirror movements in our patients were similar to those in patients associated with cervical cord lesion, but were different from those in patients associated with frontal lobe or corpus callosum lesion. It is suggested that abnormal pathways in the pyramidal tract or cervical cord lesion elicited mirror movements in our patients.

[Fisher's syndrome following Campylobacter jejuni enteritis--a case report and review of the literature]

A 13-year-old boy presented with ophthalmoplegia, cerebella ataxia and areflexia subsequent to watery diarrhea and pyrexia. Campylobacter jejuni (PEN 2: LIO 4) was isolated from the stools. The patient had a high titer of IgG anti-GQ1b IgG antibody titers which decreased during the clinical course. Although C. jejuni has recently been recognized as the most common microorganism causing infection preceding Guillain-Barré syndrome, only six patients with Fisher's syndrome after this bacterial infection have been reported. This is the first report of a patient with Fisher's syndrome in whom C. jejuni was identified as a causative organism in Japan.

Copper/topa quinone-containing histamine oxidase from Arthrobacter globiformis. Molecular cloning and sequencing, overproduction of precursor enzyme, and generation of topa quinone cofactor

The gene coding for histamine oxidase has been cloned and sequenced from a Coryneform bacterium Arthrobacter globiformis. The deduced amino acid sequence consists of 684 residues with a calculated molecular mass of 75,109 daltons and shows a high overall identity (58%) with that of phenethylamine oxidase derived from the same bacterial strain. Although the sequence similarities are rather low when compared with copper amine oxidases from other organisms, the consensus Asn-Tyr-Asp/Glu sequence, in which the middle Tyr is the precursor to the quinone cofactor (the quinone of 2,4,5-trihydroxyphenylalanine, topa) covalently bound to this class of enzymes, is also conserved in the histamine oxidase sequence. To identify the quinone cofactor, an overexpression plasmid has been constructed for the recombinant histamine oxidase. The inactive enzyme purified from the transformed Escherichia coli cells grown in a copper-depleted medium gained maximal activity upon stoichiometric binding of cupric ions. Concomitantly with the enzyme activation by copper, a brownish pink compound was generated in the enzyme, which was identified as the quinone of topa by absorption and resonance Raman spectroscopies of the p-nitrophenylhydrazine-derivatized enzyme and found at the position corresponding to the precursor Tyr (Tyr-402). Therefore, the copper-dependent autoxidation of a specific tyrosyl residue operates on the formation of the topa quinone cofactor in this enzyme, as recently demonstrated with the precursor form of phenethylamine oxidase (Matsuzaki, R., Fukui, T., Sato, H., Ozaki, Y., and Tanizawa, K. (1994) FEBS Lett. 351, 360-364).

Antiischemic effects of nicorandil during coronary angioplasty in humans

The present study was undertaken on 10 patients with angina undergoing percutaneous transluminal coronary angioplasty. The angioplasty procedure consisted of two successive 30-second balloon inflations at 5 minute intervals. After the first inflation, nicorandil (0.1 mg/kg) was given intravenously over a 2-minute period. The second inflation was then performed 3 minutes after the completion of drug administration. Myocardial ischemia was measured as the magnitude of ST-segment elevation on the intracoronary electrocardiogram (intracoronary ECG) recorded from the guidewire. Nicorandil significantly reduced the magnitude of ST-segment elevation. Nicorandil did not change the heart rate-blood pressure product, nor the oxygen saturation of the blood sampled from the great cardiac vein, nor the velocity of coronary blood flow in those patients with no evidence of collaterals. These results favor the conclusion that nicorandil prolongs the intrinsic ability of cardiac myocyte to withstand oxygen deprivation. This salutary effect is possibly due to a direct cellular mechanism because nicorandil did not modify the peripheral and coronary hemodynamic parameters that govern myocardial oxygen consumption.

Doctor-shopping patients and users of alternative medicine among Japanese primary care patients

To describe the clinical characteristics of patients with doctor-shopping behavior (doctor-shopping patients) and users of alternative medicine among Japanese primary care patients, 1088 patients from the general medicine outpatient clinic of a medical school hospital answered an original questionnaire and 30-item General Health Questionnaire (GHQ). A random sample of patients was questioned in accordance with the Diagnostic Interview Schedule modified for use in Japan (DIS-JM). Twenty-three percent of these patients met our criteria for doctor-shopping patients, and 7.9% had used alternative medicine. Multivariate analysis showed no significant difference between the two groups of patients with regard to sex, age, residence, occupation, education, or marital status. The most striking characteristics of doctor-shopping patients were chronicity of illness (p < 0.005), inability to understand doctors' explanations (p < 0.005), disbelief of the doctor's diagnosis and treatment (p < 0.005), and high GHQ scores (p < 0.05). The major factor for alternative medicine users was high expectations of medical school hospitals (p < 0.01). DIS-JM interviews showed that doctor-shopping patients had a high lifetime prevalence of mental disorders. The lifetime prevalence of DSM-III somatization disorders was significantly higher in the two study groups. These results suggest that the risk factors for doctor shopping are strongly associated with chronic conditions and the doctor-patient relationship. Also, users of alternative medicine had high expectations of medical school hospitals as the symbol of modern medicine. Therefore, we emphasize the importance of accurate explanations and maintenance of good doctor-patient relationships by physicians providing care. We also suggest that when obtaining the patient's medical history, doctors ask how many prior visits the patient has made to medical facilities with the same complaint, and how many times the patient has used alternative medicine.

[Health appraisal for work adjustment of freshmen employees--information on health checkup just after entering the corporation and condition in the next fiscal year]

In 1990, 365 (males: 197, females: 168) freshmen employees at the headquarters of a large corporation were examined just after being hired in order to observe their health status. We collected (1) data of physical examinations and questionnaires for symptoms as an ordinary health checkup, (2) information on work adjustment, life patterns, and personal characteristics through interviews conducted by ten public health nurses, and (3) personal records, e.g. birth year. Statistical analyses revealed some notable findings as follows: (1) subjects with higher blood pressure had higher scores of extrovert personality among males, (2) female subjects with greater body mass index had higher scores in such manifestations of personal characteristics such as aggression and discontent with superiors, (3) higher scores of personal characteristics were noted among female subjects working in technical sections, (4) positive correlation between the scores of work adjustment and personal characteristics, (5) higher scores of undesirable life patterns among males and of work maladjustment among elder females, (6) unbalanced meal quality of subjects from rural areas, (7) higher mental tension among younger males from rural areas, and (8) higher scores of dependency and lower morale among younger female subjects. Information on health problems was collected over the 1.5 yrs that followed. More problems were detected among females than among males and among younger females than among elder females. Longitudinal analysis was carried out from just after entry into the company for approximately 1.5 yrs. Health problems in females could be predicted by the data on personal characteristics and work adjustment just after entry. Risk of health problems in male freshmen employees with hobbies and unhealthy drinking habits over the 1.5 yrs that followed was higher than in others. It was concluded that a health interview for freshmen employees by public health nurses is valuable for health care, obtaining information regarding work adjustment, life patterns, and personal characteristics.

[Evaluation of late potentials in patients with acute myocardial infarction--relationship with right ventricular infarction]

Late Potential (LP) is known to be easily detected in inferior myocardial infarction (AMI) patients. And it is also well known that high incidence of LP positive in the patients with arrhythmogenic right ventricular dysplasia are seen. However, there is no report that LP in patients with right ventricular (RV) infarction is easily detectable. This following study was conducted to distinguish how LP was affected by RV infarction. 36 inferior AMI patients (27 male, 9 female) who were performed PTCA in acute stage were selected. They were divided into three groups in accordance to the position of infarct related artery (Group A is proxysmal RCA, Group B is distal RCA and Group C is LCx). There were no significant difference among these groups in terms of filtered QRS duration and last 40 msec RMS voltage. It was concluded that RV infarction could not affect to the rate of LP positive in inferior AMI patients.

[Application of quantitative assay for endotoxin using immobilized histidine and filtration plate to parenteral drugs]

We improved the Limulus amebocyte lysate (LAL) test for endotoxins in parenteral drugs using immobilized histidine and a filtration plate. In order to deal with many samples at the same time and to apply to a routine assay, we used a filtration plate having 96 wells instead of a filter unit with a working volume of 2 ml. LAL test-affecting substances which are contained in a parenteral drug were separated from endotoxins by adsorbing endotoxins on immobilized histidine in the well of a filtration plate. Then the absorbed endotoxins were allowed to react with LAL reagent in the same well. We defined that this method had the higher precision than conventional methods and was not influenced by the concentrations of endotoxin and parenteral drugs. Hence we examined the recovery of endotoxin spiked to 23 kinds of parenteral drugs by this method, as a result, 100 +/- 25% of recovery was obtained from 17 kinds of them.

[Noninvasive technique for detection of electrical activity from the region of the bundle of His using by signal-averaged electrocardiographic system]

Recently, signal-averaging technique of high resolution electrocardiogram to detect electrical activity from the region of the bundle of His has developed. But this technique has not been commonly used for detection of His bundle activity, compare it with detection of late potentials. We studied suitable lead system, filters, signal averaging counts and high resolution gain to detect surface recording of His bundle activity. We also studied that if we recorded electrogram using late potential detection system, how many people could be detected for His bundle activity. Signal-averaging technique of high resolution electrocardiogram clinically applicated especially in atrio-ventricular block patients. There were significant changes in the frequency of identifying His bundle activity by signal-averaging electrocardiographic system recorded by varying leads system, filters, averaging counts, high resolution gain. When using this technique in a clinical situation, we should use most appropriate device, including its condition.

Evaluation of influential factors of cognitive impairments in idiopathic Parkinson's disease

Using multivariate analysis, we investigated the influence on cognitive functions of aging, brain atrophy, incidental cerebral hyperintensities (CHs), medication, and severity, duration and the initial symptoms of the disease in 53 patients with idiopathic Parkinson's disease (PD). We semiquantitatively assessed the degree of brain atrophy and CHs based on previously established methods. Cognitive functions were significantly and diffusely impaired in PD when compared with controls who were matched for age as well as for the degree and location of CHs. Patients with PD, however, had larger ventricles. Prefrontal dysfunctions were associated with a variety of predictors such as CHs, brain atrophy, severity of PD and medication whereas dorsolateral frontal functions were related simply to age and CHs in the periventricular region. Posterior brain functions had association with severity of illness, ventricular dilatation and total CH score. Clinically observed cognitive impairments in PD may consist of cognitive defects intrinsic to the disease which are variously modified by these factors. It is essential to consider all these predictors simultaneously in any discussion of cognitive functions in PD.

Informative usefulness of age, sex and vital signs in the differential diagnosis of disturbed consciousness among 175 emergency outpatients

Final diagnoses were determined among 175 emergency patients with disturbed consciousness with a Glasgow Coma Scale (GCS) of less than 15 and diagnostic usefulness of basic information was assessed using clinico-epidemiological indices. Subject patients included 98 males and 77 females with average age 53.4 years. Final diagnoses were as follows: intracranial lesions in 69 patients (39.4%), metabolic and systemic diseases in 97 (55.4%), mental diseases in 4 (2.3%), and diseases of unknown origin in 5 (2.9%). Cerebrovascular disorders and epilepsy were most frequent among the intracranial lesions, and poisoning, hypoglycemia, acute alcoholism and hypoxic encephalopathy among the metabolic and systemic diseases. Informative usefulness of age, sex and vital sings in diagnosing cerebrovascular disorders was analyzed with the use of ROC curves, showing that cut-off points of age over 60 years and of systolic blood pressure greater than 160 mmHg were most useful.

Identification of active site lysyl residues of phenylalanine dehydrogenase by chemical modification with methyl acetyl phosphate combined with site-directed mutagenesis

A monoanionic acetylation reagent, methyl acetyl phosphate, was used to acetylate lysyl residues of the recombinant thermostable phenylalanine dehydrogenase from Thermoactinomyces intermedius. The enzyme was irreversibly inactivated with the reagent in a time- and dose-dependent manner. Simultaneous addition of substrate and coenzyme markedly protected the enzyme from inactivation. Acetylated lysyl residues presumably occurring at the active site were determined by differential modification; the enzyme was first modified with a cold reagent in the presence of both substrate and coenzyme and, after removal of the added substances by gel filtration, was then labeled with a radioactive reagent. At least 7 lysyl residues per enzyme subunit were radiolabeled by this method. To further specify the lysyl residue(s) whose modification results in inactivation of the enzyme, 5 lysyl residues highly conserved in various amino acid dehydrogenase sequences were replaced with Ala by site-directed mutagenesis. Although all of the single mutant enzymes were inactivated with the reagent as effectively as the wild-type enzyme, a double mutant enzyme in which both Lys-69 and Lys-81 were replaced with Ala was found to be inactivated very slowly. These results suggest that the reagent can acetylate both of these lysyl residues and inactivate the enzyme. Kinetic analyses of the single Lys-69 and Lys-81 mutant enzymes revealed that they are involved in substrate binding and catalysis, respectively, like the corresponding residues in the homologous leucine dehydrogenase.

[Molecular biology of L-histidine decarboxylase]

L-Histidine decarboxylase (HDC) catalyzes the formation of histamine from L-histidine. This biogenic amine is known to exert various effects in physiological and pathological reactions. In contrast to the well-known mechanism of histamine action through its interaction with specific receptors, the mechanisms regulating HDC gene expression are not elucidated. We have purified HDC from mouse mastocytoma cells, and isolated mouse HDC cDNA, and found that the primary translated product is posttranslationally processed to yield a mature active enzyme. In mastocytoma cells, we demonstrated that the induction of HDC activity and HDC mRNA synergistically occurred on treatment with dexamethasone+TPA, and also cAMP+Ca2+. To clarify the mechanism of up-regulation by these stimuli of the transcription of the HDC gene, we have isolated a genomic DNA clone encoding 5'-flanking region sequence and the first two exons. The transcription start site and the nucleotide sequences of the promoter regions including TATA- and GC-boxes were determined. With mastocytoma cells transiently transfected with 5' deletion constructs of HDC-CAT fusion gene, it was found that the sequences from -132 to -53 and -267 to -53 are essential for the regulatory elements involved in the increased transcription of the HDC gene with dexamethasone+TPA and cAMP+Ca2+, respectively. Furthermore, we have isolated a genomic DNA from human basophilic cells, and analysed its structure to elucidate the mechanisms regulating the tissue specificity of HDC gene expression.

Agar plate method using Lactobacillus plantarum for biotin determination in serum and urine

An improved agar plate method of biotin bioassay using Lactobacillus plantarum ATCC 8014 and bromocresol purple was established to determine biotin levels in human serum and urine. Samples were treated with 4.5 N H2SO4 to liberate free biotin, autoclaved for 1 h and neutralized by 4.5 N NaOH, then 10 microliters was added to wells in each plate. The biotin levels were measured in 190 serum and 59 urine samples, and the means were 2.7 +/- 0.53 ng/ml and 12.4 +/- 5.56 ng/mg of creatinine, respectively. The intra-assay coefficient varience (CV) were 3.2 (n = 20) and 1.3% (n = 23), respectively. The recovery of biotin added (10 ng/ml) to serum was 110.7%, and to urine was 99.6%. These findings suggest that this assay is sufficiently accurate and reproducible for routine use in the clinical laboratory. The excretion of orally administered biotin was also demonstrated by the method.

Generation of the topa quinone cofactor in bacterial monoamine oxidase by cupric ion-dependent autooxidation of a specific tyrosyl residue

The quinone of 2,4,5-trihydroxyphenylalanine (topa), recently identified as the covalently bound redox cofactor in copper amine oxidases, is encoded by a specific tyrosine codon. To elucidate the mechanism of its formation, the recombinant phenylethylamine oxidase of Arthrobacter globiformis has been overproduced in Escherichia coli and purified in a Cu(2+)-deficient form. The inactive precursor enzyme thus obtained was dramatically activated upon incubation with Cu2+, concomitantly with the formation of the topa quinone at the position corresponding to Tyr382, occurring in the tetrapeptide sequence highly conserved in this class of enzymes. The topa quinone was produced only under aerobic conditions, but its formation required no external enzymatic systems. These findings demonstrate the Cu(2+)-dependent autooxidation of a specific tyrosyl residue to generate the topa quinone cofactor.

Affinity labeling of the two species of Escherichia coli lysyl-tRNA synthetase with adenosine di- and triphosphopyridoxals

Lysyl-tRNA synthetase (LysRS), a representative of the class 2 aminoacyl-tRNA synthetases, occurs as two species in Escherichia coli: LysRSs and LysRSu. To identify the ATP-binding site in this enzyme, we have applied affinity labeling with reactive adenine nucleotide analogs. Incubation of either enzyme species with adenosine di- or triphosphopyridoxal, followed by borohydride reduction, resulted in a time-dependent incorporation of the reagent, accompanied with the loss of both tRNA(Lys) aminoacylation, and lysine-dependent isotopic ATP-PPi exchange activities. LysRSu appeared less sensitive to adenosine triphosphopyridoxal than LysRSs. Complete inactivation with either reagent corresponded to the incorporation of about 2 mol of reagent per mol of dimeric enzyme. MgATP and ATP protected both enzyme species against the inactivation, suggesting that the modification occurs at the ATP-binding site. Sequence analysis of the labeled peptide isolated from the inactivated LysRSs and LysRSu revealed that bulk of the label was distributed among six lysyl residues at positions 25, 82, 114, 156, 364, and 505, with preference for Lys-114 and Lys-156. In LysRSs, Lys-132 and Lys-185 were also modified by both reagents, although these residues are not conserved in LysRSu. It is concluded that the folding of the LysRSs and LysRSu polypeptides and the relative locations of the identified lysyl residues with respect to the binding site for the two labels are very similar.

Affinity labeling of Escherichia coli lysyl-tRNA synthetase with pyridoxal mono- and diphosphate

Pyridoxal 5'-phosphate (PLP) and pyridoxal 5'-diphosphate (PLDP) were used to identify lysyl residues at the phosphate-binding locus in the lysS-encoded and the lysU-encoded lysyl-tRNA synthetases (LysRSs and LysRSu, respectively) from Escherichia coli. Incubation of LysRSs with either reagent, followed by borohydride reduction, resulted in a time-dependent covalent incorporation of the reagent, accompanied with the loss of both tRNA(Lys) aminoacylation and lysine-dependent ATP-PPi exchange activities. By contrast, LysRSu activity was insensitive to prolonged incubation with either reagent, possibly reflecting a difference at the phosphate-binding locus in the two enzyme species. MgATP protected LysRSs against inactivation by PLP or PLDP. Complete inactivation of LysRSs corresponded to the incorporation of 2.6 +/- 0.1 mol of PLP or PLDP per mol of dimeric enzyme. Either reagent was found to label the same set of eight lysyl residues (Lys-25, Lys-82, Lys-114, Lys-132, Lys-156, Lys-185, Lys-364, and Lys-505) as adenosine di- or triphosphopyridoxal (see the preceding paper in this issue). These lysyl residues might represent the subsite for the phosphate moiety of ATP in LysRSs. None of the identified lysyl residues is located within the three sequence motifs considered as characteristic of the class 2 aminoacyl-tRNA synthetases. The present results are discussed on the basis of the crystalline structure of the closely related aspartyl-tRNA synthetase from Saccharomyces cerevisiae.

Association of N-ethylmaleimide-sensitive factor with synaptic vesicles

N-Ethylmaleimide-sensitive factor (NSF) mediates docking and/or fusion of transport vesicles in the multi-pathways of vesicular transport. NSF was highly expressed in brain and adrenal gland. Immunostaining of cerebellum with an anti-NSF monoclonal antibody showed that NSF is predominantly localized in the molecular layers and the glomeruli of the granule cell layers. This distribution coincided well with that of synaptophysin, a marker protein of synaptic vesicles. Purification and immunoprecipitation revealed that NSF is associated with brain synaptic vesicles. The present results suggest that NSF is associated with synaptic vesicles without Ca2+ influx.