Amino acid sequence of the active site of human pseudocholinesterase

The usualE ₁ ^u and atypicalE ₁ ^a human pseudocholinesterases (acylocholine acylhydrolase, EC 3.1.1.8) were purified to homogeneity. The active-site serine residue was conjugated with diisopropyl fluorophosphate and digested with trypsin. The tryptic peptide containing the active site was isolated by gel filtration followed by two-dimensional paper chromatography and electrophoresis. The amino acid sequence of the active site peptide obtained from the usualE ₁ ^u enzyme was found to be Gly-Glu-Ser-Ala-Gly-Ala-Ser-Ala-Val-Ser-Leu. A remarkable structural homology exists between the human and the horse enzymes in their active sites. From the difference in electrophoretic mobility of the active-site peptides obtained from the usual and atypical enzymes, the probable structure of the atypical human enzyme was deduced as Gly-His-Ser-Ala-Gly-Ala-Ser-Ala-Val-Ser-Leu.     

DEVELOPMENT, SEXUAL DIMORPHISM, and INDIVIDUAL VARIATION IN THE SKELETON OF THE FINLESS PORPOISE, NEOPHOCAENA PHOCAENOIDES, IN THE COASTAL WATERS OF WESTERN KYUSHU, JAPAN

Development, sexual dimorphism, and individual variation were examined in the skeleton of the finless porpoise in the coastal waters of western Kyushu, Japan. Skulls ceased growing by 4 yr. Postcranial skeletons ceased increasing in size at an age older than 11 yr. The finless porpoise was estimated to attain cranial maturity by 4 yr and physical maturity at 14–23 yr. Sexual dimorphism was not detectable in most of the cranial characters but was detected in more than half of the postcranial characters. Females tended to show larger values of postcranial characters. The shape of the pelvic bone was obviously different between males and females. Thus, a discriminant function was proposed to determine sex using measurements of this bone. Individual variation was greatest in the feeding apparatus such as length of the rostrum, and least in the braincase.     

Studies on the Radioresistance of Bacillus Spores

Radioresistance of the spores of 46 strains of Bacillus was determined based on their dose-survival curves. The spores were produced on three kinds of sporulating medium.

The variations in the radioresistance among species and strains were found, and also the radioresistance of spores depended upon the sporulating medium. The shapes of dose-survival curves are closely associated with the taxonomical groups of the genus Bacillus.

Radioresistance of the spores showed no apparent correlation to their contents of dipicolinic acid, calcium and magnesium, but a slight correlation was observed between radioresistance and the molar ratio of Ca to DPA or Mg to Ca. Radioresistance of the spores in some groups correlated to their GC content, but no correlation was found in the other species. There was no correlation between heat resistance and radioresistance.     

Nonadrenergic inhibitory nerves attenuate neurally mediated contraction in cat bronchi

Effects of nonadrenergic and noncholinergic (NANC) inhibitory nerves on cholinergic neurotransmission were examined in isolated bronchial segments from cats in the presence of propranolol (10(-6) M) and indomethacin (10(-6) M) by use of electrical field stimulation (EFS) techniques. EFS caused contraction alone in tissues at the baseline tension and biphasic responses (contraction and relaxation) in tissues precontracted with 5-hydroxytryptamine. Contraction was abolished by atropine (10(-6) M), and relaxation was abolished by tetrodotoxin (10(-6) M). At the baseline tension, EFS at frequencies greater than 10 Hz inhibited the subsequent (4 min later) contraction induced by EFS at 1-5 Hz. EFS-induced inhibition was stimulus frequency dependent and reached maximum at 20 Hz. However, EFS at 20 Hz did not inhibit the subsequent contractile response to acetylcholine (10(-7) to 10(-3) M). Exogenously applied vasoactive intestinal peptide mimicked EFS-induced inhibitory effects, but substance P and calcitonin gene-related peptide did not. The inhibitory effect of EFS at 20 Hz was not altered by pyrilamine, cimetidine, naloxone, methysergide, phentolamine, BW755C, AF-DX 116, or removal of epithelium. These results imply that the NANC transmitter acts via presynaptic cholinergic receptors.     

Kinetic Properties of a Dipeptidase from Streptococcus cremoris

Some kinetic properties of a dipeptidase purified from a cell-free extract of Streptococcus cremoris H 61 were investigated. The Km values of this enzyme for various dipeptides were divided into 3 groups. Group 1 comprised mainly of neutral dipeptides, such as Leu-Gly, Leu-Leu and Leu-Ala, which had relatively low Km values (in the range 4.0-6.6 mm). Group 2 consisted of dipeptides with aromatic large amino acids either at the N- or C-terminal positions, like Leu-Phe, Phe-Ala and Leu-Tyr, which had very low Km values (in the range 1.0-2.4 mm). Group 3 was made up by dipeptides with acidic or basic amino acids at the N-terminals; His-Ala and Glu-Val were typical of this group. These had very high Km values (in the range 10–20 mm). Substantial substrate competition was found to exist in the presence of His-Ala. Bestatin inhibited the enzyme competitively with Leu-Gly and was found to have an apparent Ki value of 3.0 × 10^?8 m for the enzyme. Further, the enzyme was completely inhibited by EDTA at a concentration of 2.0 × 10^?5 m. On the other hand, once the activity was inhibited by EDTA, it could be restored by Co²⁺ and Zn²⁺ in the acidic pH side, and by Ca²⁺ and Mn²⁺ in the alkaline pH side.     

Isolation and Characterization of Two Plasmids in Bacillus subtilis var. amylosacchariticus

Five bufadienolides (1-5) isolated from the leaves of Kalanchoe pinnata and K. daigremontiana×tubiflora (Crassulaceae) were examined for their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation in Raji cells induced by the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate. All bufadienolides showed inhibitory activity, and bryophyllin A (1) exhibited the most marked inhibition (IC₅₀=0.4 μM) among the tested compounds. Bryophyllin C (2), a reduction analogue of 1, and bersaldegenin-3-acetate (3) lacking the orthoacetate moiety were less active. These results strongly suggest that bufadienolides are potential cancer chemopreventive agents.     

Conformational changes of α-lactalbumin induced by the stepwise reduction of its disulfide bridges: The effect of the disulfide bridges on the structural stability of the protein in sodium dodecyl sulfate solution

Four disulfide bridges of bovineα-lactalbumin (α-lact) were selectively reduced to obtain its derivatives with three, two, and zero disulfide bridges (designated as 3SS, 2SS, and OSSα-lact, respectively). The original helicity was almost maintained in 3SSα-lact missing only the Cys6-Cysl20 bridge. Upon the reduction of both Cys28-Cys111 and Cys6-Cys120 bridges, various changes occurred in the protein. In particular, the maximum fluorescence of 1-anilinonaphthalene-8-sulfonic acid was observed in this stage. Upon the reduction of all disulfide bridges, the hydrophobic box of the protein, formed by Trp60, Ile95, Tyr103, and Trp104, was disrupted and an internal helical structure was destroyed. The conformation of each derivative was examined mainly in a solution of sodium dodecyl sulfate. In the surfactant solution, the helicity increased from 33% to 37% in 3SSα-lact, from 26% to 31% in 2SSα-lact, and from 18% to 37% in OSSα-lact, as against from 34% to 44% in intactα-lact. On the other hand, the tryptophan fluorescence of each derivative was affected in very low surfactant concentrations, suggesting that the tertiary structure considerably changed prior to the secondary structural change in the surfactant solution.     

Development of simultaneous gas chromatography-mass spectrometric and liquid chromatography-electrospray ionization mass spectrometric determination method for the new designer drugs, N-benzylpiperazine (BZP), 1-(3-trifluoromethylphenyl)piperazine (TFMPP) and their main metabolites in urine

To prove the intake of recently controlled designer drugs, N-benzylpiperazine (BZP) and 1-(3-trifluoromethylphenyl)piperazine (TFMPP), a simple, sensitive and reliable method which allows us to simultaneously detect BZP, TFMPP and their major metabolite in human urine has been established by coupling gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). GC-MS accompanied by trifluoroacetyl (TFA) derivatization and LC-MS analyses were performed after the enzymatic hydrolysis and the solid phase extraction with OASIS HLB, and BZP, TFMPP and their major metabolites, 4'-hydroxy-BZP (p-OH-BZP), 3'-hydroxy-BZP (m-OH-BZP) and 4'-hydroxy-TFMPP (p-OH-TFMPP), have found to be satisfactorily separated on a semi-micro SCX column with acetonitrile-40 mM ammonium acetate buffer (pH 4) (75:25, v/v) as the eluent. The detection limits produced by GC-MS were estimated to be from 50 ng/ml to 1 microg/ml in the scan mode, and from 200 to 500 ng/ml in the selected ion monitoring (SIM) mode. Upon applying the LC-ESI-MS technique, the linear calibration curves were obtained by using the SIM mode for all analytes in the concentration range from 10 ng/ml to 10 microg/ml. The detection limits ranged from 5 to 40 ng/ml in the scan mode, and from 0.2 to 1 ng/ml in the SIM mode. These results indicate the high reliability and sensitivity of the present procedure, and this procedure will be applicable for proof of intake of BZP and TFMPP in forensic toxicology.     

The Kinetochore Protein Kis1/Eic1/Mis19 Ensures the Integrity of Mitotic Spindles through Maintenance of Kinetochore Factors Mis6/CENP-I and CENP-A

Microtubules play multiple roles in a wide range of cellular phenomena, including cell polarity establishment and chromosome segregation. A number of microtubule regulators have been identified, including microtubule-associated proteins and kinases, and knowledge of these factors has contributed to our molecular understanding of microtubule regulation of each relevant cellular process. The known regulators, however, are insufficient to explain how those processes are linked to one another, underscoring the need to identify additional regulators. To find such novel mechanisms and microtubule regulators, we performed a screen that combined genetics and microscopy for fission yeast mutants defective in microtubule organization. We isolated approximately 900 mutants showing defects in either microtubule organization or the nuclear envelope, and these mutants were classified into 12 categories. We particularly focused on one mutant, kis1, which displayed spindle defects in early mitosis. The kis1 mutant frequently failed to assemble a normal bipolar spindle. The responsible gene encoded a kinetochore protein, Mis19 (also known as Eic1), which localized to the interface of kinetochores and spindle poles. We also found that the inner kinetochore proteins Mis6/CENP-I and Cnp1/CENP-A were delocalized from kinetochores in the kis1 cells and that kinetochore-microtubule attachment was defective. Another mutant, mis6, also displayed similar spindle defects. We conclude that Kis1 is required for inner kinetochore organization, through which Kis1 ensures kinetochore-microtubule attachment and spindle integrity. Thus, we propose an unexpected relationship between inner kinetochore organization and spindle integrity.