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N Tamiya

Publications and source records attributed to N Tamiya.

At least 55 records · Page 3Linked to original sources
PubMed1986

Proton nuclear magnetic resonance analyses of the molecular conformations of unique long neurotoxins bearing Phe-25: Astrotia stokesii b, Astrotia stokesii c, and Acanthophis antarcticus b.

The 270-MHz proton NMR spectra of the unique long neurotoxins bearing Phe-25, Astrotia stokesii b (As b) and Astrotia stokesii c (As c) from Astrotia stokesii, and Acanthophis antarcticus b (Aa b) from Acanthophis antarcticus, have been analyzed. The aromatic proton resonances of Phe-25 in As b and Aa b were assigned on the basis of the nuclear Overhauser effects observed on irradiation of slowly exchanging amide protons. Phe-25 was found to be involved in hydrophobic interactions with Ile/Val-42, Ala-46 and Ile-58 in As b and As c, and with Ala-46 and Val-58 in Aa b. These hydrophobic interactions, instead of the hydrogen bond between Tyr-25 and Glu-42 found in other neurotoxins, appear to be important for maintenance of the biologically active tertiary structure. The pH dependency of the chemical shift and intensity of the Trp-72 N-1 proton resonance of As b indicates that the indole ring is not fully exposed to the solvent and that the extra tail segment of this long neurotoxin interacts with the main part of the molecule.

Circular Dichroism↗
PubMed1985

Isolation and amino acid sequence of a short-chain neurotoxin from an Australian elapid snake, Pseudechis australis.

A short-chain neurotoxin Pseudechis australis a (toxin Pa a) was isolated from the venom of an Australian elapid snake Pseudechis australis (king brown snake) by sequential chromatography on CM-cellulose, Sephadex G-50 and CM-cellulose columns. Toxin Pa a has an LD50 (intravenous) value of 76 micrograms/kg body wt. in mice and consists of 62 amino acid residues. The amino acid sequence of Pa a shows considerable homology with those of short-chain neurotoxins of elapid snakes, especially of true sea snakes.

Amino Acid Sequence↗
PubMed1985

Acetylcholine receptors of human skeletal muscle: a species difference detected by snake neurotoxins.

The binding abilities of the nicotinic acetylcholine receptors (AChRs) of the skeletal muscles of man and other vertebrates to two typical curaremimetic toxins, erabutoxin b (Eb) and alpha-bungarotoxin (alpha-BT), were investigated. Fluorescent microscopy using rhodamine-labeled erabutoxin b (TMR-Eb) and FITC-labeled alpha-bungarotoxin (FITC-alpha-BT) revealed that AChRs of human and chimpanzee muscles were stained with FITC-alpha-BT, but not with TMR-Eb. In contrast, the AChRs of mouse muscle were stained with both fluorescent toxins. The stainings of human and chimpanzee AChRs with FITC-alpha-BT were inhibited by preincubation with unmodified alpha-BT, but not with either unmodified Eb or other short-chain neurotoxins. Binding experiments using 125I-labeled Eb ([125I]Eb) and 125I-labeled alpha-BT ([125I]alpha-BT) showed that the affinity of human AChRs for [125I]Eb was unusually low. Electrophysiological experiments showed that both acetylcholine potential and end-plate potential of human muscle were blocked by addition of alpha-BT, but not by Eb. On the contrary, acetylcholine potential of rat muscle was blocked by addition of Eb. All these results indicate that AChRs of human and chimpanzee muscles are different from those of other animals in having an exceptionally low affinity for Eb and other short-chain neurotoxins. The results suggest a heterogeneity among vertebrate AChRs concerning their reactivities to curaremimetic toxins.

Animals↗
PubMed1985

Amino acid sequence of a sea anemone toxin from Parasicyonis actinostoloides.

Amino-acid sequence of a toxin from sea anemone, Parasicyonis actinostoloides, is determined. The toxin consists of 31 amino acid residues and is cross-linked with four disulphide bridges. The sequence has some similarity to that of toxin III and no similarity to those of toxin I and toxin II both from sea anemone, Anemonia sulcata, or to that of Anthopleurin A from Anthopleura xanthogrammica.

Amino Acid Sequence↗
PubMed1985

Isolation and properties of two phospholipases A2 from the venom of an Australian elapid snake (Pseudechis australis).

Two phospholipases A2 (Pa-11 and Pa-13) were purified from the venom of an Australian elapid snake (subfamily Acanthophiinae) Pseudechis australis (king brown snake) by chromatography on CM-cellulose CM-52 followed by gel filtration on a Sephadex G-75 column. The apparent molecular weights of the two phospholipases A2 (Pa-11 and Pa-13) were 14,000 and 13,500, respectively, by gel filtration analysis on a Sephadex G-75 column. Each enzyme molecule consists of a single polypeptide chain of 118 amino acid residues. The isoelectric points of Pa-11 and Pa-13 were 10.5 and 10.0, respectively. The optimum pH values of Pa-11 and Pa-13 for hydrolysis of egg-yolk phosphatidylcholine were 7.8 and 7.5, respectively. Pa-11 was lethal to mice (LD50 0.23 micrograms/g body weight), whereas Pa-13 showed no lethal activity at a dose level of 7.4 micrograms/g mouse. Each enzyme was inactivated by reaction with p-bromophenacylbromide on the sole histidine residue (Pa-11) or on one of the two histidine residues (Pa-13). Oxidation of the tryptophan residues in Pa-11 and Pa-13 with N-bromosuccinimide led to a decrease in the phospholipase A activity. A complete loss of both enzymic and lethal activities of Pa-11 was observed upon oxidation of one of the two tryptophan residues of the molecule.

Acetophenones↗
PubMed1985

Amino acid sequences of phospholipases A2 from the venom of an Australian elapid snake (king brown snake, Pseudechis australis).

Two basic phospholipases A2 (Pa-11 and Pa-13) have been isolated from the venom of an Australian elapid snake, Pseudechis australis (king brown snake). The reduced and S-carboxymethylated phospholipases A2 were digested with trypsin and the resulting peptides were purified by a combination of chromatography on a DEAE-cellulose DE-52 column and gel filtration procedures. Eleven main peptides from Pa-11 and 9 peptides from Pa-13 could account for the amino acid compositions of the respective enzyme molecules. The alignment of the tryptic peptides and unelucidated regions of the amino acid sequences of tryptic peptides were established by the analysis of the peptides obtained by chymotryptic and/or Staphylococcal protease digestions. Each phospholipase A2 consisted of a single chain of 118 amino acid residues, including 14 half-cystine residues. Although Pa-11 is enzymatically 30-times as active as Pa-13 and highly toxic as compared to Pa-13, they are highly homologous in their amino acid sequences. They are also homologous to the enzymes from mammalian pancreas and the other snake venom phospholipases A2, especially to those from snakes belonging to the subfamilies Acanthophiinae and Laticaudinae.

Amides↗
PubMed1985

Non-divergence theory of evolution: sequence comparison of some proteins from snakes and bacteria.

A "non-divergence theory" is proposed for the mechanism of evolution. The theory is based on the observation that comparison of the amino acid sequences of related proteins in various organisms gives inconsistent results from one type of protein to another, and on the occurrence of significant gene transfer among living organisms. Special attention is focused on the sequence comparisons of short- and long-chain neurotoxins and phospholipases A2 from the venoms of proteroglyphous snakes and those of microbial ferredoxins, rubredoxins, and flavodoxins.

Amino Acid Sequence↗
PubMed1984

Photochemically induced nuclear polarization study of exposed tyrosines, tryptophans, and histidines in postsynaptic neurotoxins and in membranotoxins of elapid and hydrophid snake venoms.

The accessibility of surface tyrosines, histidines, and tryptophans in snake venom neurotoxins (short and long) and in membranotoxins to excited triplet 10-(carboxyethyl)-flavin was studied by photochemically induced dynamic nuclear polarization at 270 MHz. Trp-29 is accessible in the short neurotoxins--erabutoxins a, b, and c and cobrotoxin--and also in the long neurotoxins--alpha-cobratoxin and alpha-bungarotoxin. Tyr-25 is practically inaccessible in all neurotoxins. Tyr-39 in cobrotoxin and Tyr-55 in alpha-bungarotoxin are accessible. His-6 (revised sequence) is inaccessible in the erabutoxins while His-26 is only very weakly accessible. His-22 of alpha-cobratoxin is inaccessible as are His-4 and -68 in alpha-bungarotoxin and His-4 of cobrotoxin. His-33 of cobrotoxin is accessible. The rigidity order alpha-bungarotoxin greater than or equal to alpha-cobratoxin greater than or equal to erabutoxins, with respect to the unfolding effect of 7 M urea, was deduced in this study. In the membranotoxins studied (cardiotoxin and its analogues I, II, and IV as well as cytotoxin I and II), the two tyrosines Tyr-25 and Tyr-58 are only weakly accessible. Tyr-14 is completely accessible and so is in all probability Tyr-29. These studies allow deductions to be made about the accessibilities in analogous systems. Thus, the accessibility of His-33 and the inaccessibility of His-4 in cobrotoxin can be used to deduce the conformations of these residues in a large group of neurotoxins including the alpha-toxin of Naja nigricollis, neurotoxin II of Naja naja oxiana, and neurotoxins I and III of Naja mossambica mossambica.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1983

The source of oxygen in the reaction catalysed by collagen lysyl hydroxylase.

The synthetic peptides (Pro-Pro-Gly)5 and (Ile-Lys-Gly)5-Phe were hydroxylated with collagen prolyl hydroxylase and lysyl hydroxylase in an 18O2 atmosphere. The oxygen atoms in the hydroxy groups of hydroxyproline and hydroxylysine were 87% and 6.5% respectively derived from the atmospheric 18O2. The results are consistent with those reported previously for proline hydroxylation in vivo [Fujimoto & Tamiya (1962) Biochem. J. 84, 333-335; Prockop, Kaplan & Udenfriend (1962) Biochem. Biophys. Res. Commun. 9, 192-196; Fujimoto & Tamiya (1963) Biochem. Biophys. Res. Commun. 10, 498-501; Prockop, Kaplan & Udenfriend (1963) Arch. Biochem. Biophys. 101, 499-503] and in vitro [Cardinale, Rhoads & Udenfriend (1971) Biochem. Biophys. Res. Commun. 43, 537-543] and for lysine hydroxylation in vivo [Fujimoto & Tamiya (1963) Biochem. Biophys. Res. Commun. 10, 498-501]. In view of the similarities of these two oxygenase-type hydroxylation reactions the participation of intermediates is proposed, the oxygen atoms of which are exchangeable with those of water. The atmospheric oxygen atoms incorporated into the intermediate must be equilibrated with water oxygen atoms in the slower lysyl hydroxylase reaction.

Chemical Phenomena↗
PubMed1983

Neurotoxins from the venoms of the sea snakes Hydrophis ornatus and Hydrophis lapemoides.

The main neurotoxic components, toxins Hydrophis ornatus a and Hydrophis lapemoides a, were isolated from the venoms of the sea snakes Hydrophis ornatus and Hydrophis lapemoides respectively. The amino acid sequence of toxin Hydrophis ornatus a was deduced to be identical with that of toxin Astrotia stokesii a [Maeda & Tamiya (1978) Biochem. J. 175, 507-517] on the basis of identity of the tryptic peptide 'map' and the amino acid composition of each peptide. The amino acid sequence of toxin Hydrophis lapemoides a was determined mainly on the basis of identity of the amino acid compositions, mobilities on paper electrophoresis and migration positions on paper chromatography of the tryptic peptides with those of other sea-snake toxins whose sequences are known. Both toxins Hydrophis ornatus a and Hydrophis lapemoides a consisted of 60 amino acid residues and there were six amino acid replacements between them. The taxonomy of sea snakes in the Hydrophis ornatus complex has long been confused, and the above snakes were originally assigned to taxa that proved to be inconsistent with the relationships indicated by the neurotoxin amino acid sequences obtained. A subsequent re-examination of the specimens revealed an error in the original identifications and demonstrated the value of the protein amino acid sequences in systematic and phylogenetic studies. The isolation procedure and results of amino acid analysis of the tryptic peptides have been deposited as Supplementary Publication SUP 50121 (8 pages) with the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies may be obtained as indicated in Biochem. J. (1983) 209, 5.

Amino Acid Sequence↗
PubMed1983

The neurotoxins of the sea snake Laticauda schistorhynchus.

Erabutoxins a and b, the major neurotoxins in the venom of the sea snake Laticauda semifasciata, were detected in the venom of Laticauda schistorhynchus. The identity of the toxins was confirmed on the basis of elution position on CM-cellulose column chromatography, disc electrophoretic mobility, amino acid analysis and toxicity measurement.

Amino Acids↗
PubMed1982

Amino acid sequences of three phospholipases A I, III and IV from the venom of the sea snake Laticauda semifasciata.

Amino acid sequences of three phospholipases A, I, III and IV, from the venom of the sea snake Laticauda semifasciata were elucidated. Each protein consisted of a single chain of 118 amino acid residues, including 14 half-cystine residues. They showed high homology among themselves, and with the other snake-venom phospholipases A and with the enzymes from mammalian pancreas. Phospholipases A III and IV were especially similar to each other, with only four differences out of their 118 amino acid residues. Phospholipase A I contained one tryptophan residue at position 64, which was important for enzymic activity, whereas III and IV did not contain tryptophan residues and their corresponding positions were occupied by leucine residues. The substitution by leucine resulted in a decreased, but definite, phospholipase A activity. The substituted enzymes have a more potent neuromuscular blocking activity. Full experimental details and evidence for the amino acid sequences of the proteins have been deposited as Supplementary Publication SUP 50118 (39 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem.J. (1981) 193, 5.

Amino Acid Sequence↗
PubMed1982

Amino acid sequences of two novel long-chain neurotoxins from the venom of the sea snake Laticauda colubrina.

From the venom of a population of the sea snake Laticauda colubrina from the Solomon Islands, a neurotoxic component, Laticauda colubrina a (toxin Lc a), was isolated in 16.6% (A280) yield. Similarly, from the venom of a population of L. colubrina from the Philippines, a neurotoxic component, Laticauda colubrina b (toxin Lc b), was obtained in 10.0% (A280) yield. The LD50 values of these toxins were 0.12 microgram/g body wt. on intramuscular injection in mice. Toxins Lc a and Lc b were each composed of molecules containing 69 amino acid residues with eight half-cystine residues. The complete amino acid sequences of these two toxins were elucidated. Toxins Lc a and Lc b are different from each other at five positions of their sequences, namely at positions 31 (Phe/Ser), 32 (Leu/Ile), 33 (Lys/Arg), 50 (Pro/Arg) and 53 (Asp/His) (residues in parentheses give the residues in toxins Lc a and Lc b respectively). Toxins Lc a and Lc b have a novel structure in that they have only four disulphide bridges, although the whole amino acid sequences are homologous to those of other known long-chain neurotoxins. It is remarkable that toxins Lc a and Lc b are not coexistent at the detection error of 6% of the other toxin. Populations of Laticauda colubrina from the Solomon Islands and from the Philippines have either toxin Lc a or toxin Lc b and not both of them.

Amino Acid Sequence↗
PubMed1982

[Role of lysines in the stability of a snake neurotoxin].

The effects of charge suppression at a single lysine residue on the energetics of thermal unfolding or unfolding with guanidinium chloride of erabutoxin b are studied by circular dichroism. It is shown that acylation of lysine 15, 47 or 51 has virtually no effect on the toxin stability. In contrast, abolition of the positive charge of lys-27, a residue involved in the "toxic" site of the molecule, substantially increases the toxin stability. This phenomenon is attributed to suppression of repulsive interactions occurring within the native toxin molecule between lys-27 and other positively charged groups.

Acylation↗