Synthesis and conformational analysis of aib-containing peptide modelling for N-glycosylation site in N-glycoprotein

A tetrapetide containing an Aib residue, Boc-Asn-Aib-Thr-Aib-OMe, was synthesized as a peptide model for the N-glycosylation site in N-glycoproteins. Backbone conformation of the peptide and possible intramolecular interaction between the Asn and Thr side chains were elucidated by means of n.m.r. spectroscopy. Temperature dependence of NH proton chemical shift and NOE experiments showed that Boc-Asn-Aib-Thr-Aib-OMe has a tendency to form a β-turn structure with a hydrogen bond involving Thr and Aib⁴ NH groups. Incorporation of Aib residues in the peptide model promotes folding of the peptide backbone. With folded backbone conformation, carboxyamide protons of the Asn residue are not involved in hydrogen bond network, while the OH group of the Thr residue is a candidate for a hydrogen bond in DMSO-d₆ solution.     

Synthesis of the vasoconstrictor peptide endothelin in kidney cells

The expression plasmid containing human prepro-endothelin cDNA was constructed and introduced into COS-7 cells. Mature endthelin, consisting of 21 amino acid residues, was secreted into the culture medium of the transfected cells and was also synthesized by non-transfected COS-7 cells. Normal kidney cells derived from other species also synthesized and secreted endothelin. Partial characterization of endothelins produced by kidney cells suggested that existence of new types of endothelin. This is the first report of the vasoconstrictor peptide endothelin being synthesized in kidney cells.     

EnterohemorrhagicEscherichia coli O157:H7 possesses somatic (O) antigen identical with that ofSalmonella O301

The O antigen of enterohemorrhagicEscherichia coli O157:H7 is identical with that ofSalmonella O30₁ and is also related toSalmonella O30₁30₂ in an a-a, b type of relationship.     

Unusual solvent effect on protease activity and effective optical resolution of amino acids by hydrolytic reactions in organic solvents

Summary The catalytic activities of -chymotrypsin, subtilisin Carlsberg, and subtilisin BPN' for hydrolysis of amino acid esters in acetonitrile-water were unusually dependent on the solvent composition. The products obtained as precipitates in high concentrations of acetonitrile were L-amino acids of high optical purities, and effective optical resolution of amino acids was achieved.     

Acute reversible cataract due to nitrocompounds in Japanese quail (Coturnix coturnix japonica)

The present study was designed to examine the usefulness of the Japanese quail as an experimental model of cataractogenic activity. Chemicals, 2, 6-dibromo-4-nitro-phenol (2, 6-D), 2, 4-dinitroanisole (2, 4-DA), and 2, 4-dinitrophenol (2, 4-D; for the positive control), were administered singly through an oral route to 2-week old male Japanese quails to investigate the reversibility of cataracts. A single administration of 2, 4-D (36 and 43 mg/kg) produced reversible cataract in 14 of 16 animals (87.5%). This cataract was seen 1 or 2 hours after treatment and continued for 1 to 12 hours. Treatment with 2, 6-D (20 and 25 mg/kg) and 2, 4-DA (120 and 150 mg/kg) caused cataracts in 7 of 11 (63.6%) and 8 of 8 surviving animals (100%), respectively. Cataracts produced by 2, 6-D and 2, 4-DA, which were observed from 1 and 2 to 4 hours after the treatment, continued for 6 to 15 and 1 to 13 hours, respectively. Mortalities in the 25 mg/kg group of 2, 6-D, 120 mg/kg and 150 mg/kg group of 2, 4-DA were found in 2 of 5 animals, 1 of 5 animals and 5 of 9 animals, respectively. These results indicate that the Japanese quail is useful as an animal model to evaluate toxicity to the eye and cataractogenesis.     

Induction of SOS functions by nitrogen dioxide in Escherichia coli with different DNA-repair capacities

The effect of gaseous nitrogen dioxide (NO2) on cytotoxicity, induction of synthesis of UmuC and RecA proteins, and mutagenesis was studied in Escherichia coli strains with different capacities of DNA repair. Gaseous NO2 (90, 180 microliter/l) killed Escherichia coli. The recA mutant was most sensitive, the lexA mutant moderately sensitive, and the uvrA mutant and the wild-type the least sensitive. When 90 microliter/l NO2 gas was bubbled into bacterial suspensions for 30 min at a flow rate of 100 ml/min, the induction of umuC gene expression increased in the wild-type strain. NO2 also induced the recA gene expression in the wild-type strain. The synthesis of neither RecA nor UmuC proteins was induced in the recA and lexA mutants. We further investigated the NO2 mutagenesis in the cells treated with bubbling of NO2 gas. NO2 caused mutation to Trp+ of WP2.     

Purification and characterization of a lectin from the beetle, Allomyrina dichotoma

A lectin was purified from the hemolymph of Allomyrina dichotoma larvae by affinity chromatography on acid-treated Sepharose 4B. The purified lectin showed two protein bands on polyacrylamide gel electrophoresis. These two lectin bands (allo A-I and -II) were separated by DEAE-Cellulofine column chromatography. By gel filtration on Sephadex G-100, the molecular weights of allo A-I and -II were estimated to be 65,000 and 66,500, respectively. On the other hand, by SDS-polyacrylamide gel electrophoresis after cross-linking of subunits with glutaraldehyde, they are estimated to be 38,000 and 39,000, respectively. On SDS-polyacrylamide gel electrophoresis, it was proved that both allo A-I and -II lectin consisted of two subunits, respectively. The molecular weights were 17,500 and 20,000 for allo A-I, and 19,000 and 20,000 for allo A-II. The isoelectric points of allo A-I and -II were estimated to be 6.4 and 5.9, respectively. On double immunodiffusion, allo A-I and -II gave single precipitin lines, which fused completely with each other, against the antibody to crude allo A. The hemagglutinating activity of allo A-I and -II was inhibited only by beta-linked D-galactose such as lactose and lactulose.     

A novel opioid peptide, leumorphin, acts as an agonist at the kappa opiate receptor

The primary structure of the common precursor of porcine beta-neo-endorphin and dynorphin (preproenkephalin B) has shown the existence of a third leucine-enkephalin (leu-enkephalin) sequence with a C-terminal extension of 24 amino acids. This nonacosapeptide, named leumorphin, was approximately 70 times more potent than leu-enkephalin in inhibiting the contraction of the myenteric plexus-longitudinal muscle preparation of the guinea pig ileum. This action of leumorphin, like those of beta-neo-endorphin and dynorphin, was antagonized less effectively by naloxone than that of leu-enkephalin, but more effectively by Mr2266, an antagonist relatively specific for the kappa type opiate receptor. The inhibitory action of leumorphin or beta-neo-endorphin on the contraction of the guinea pig ileum muscle strip was reduced in a dose-dependent manner by pretreatment with dynorphin and vice versa. Leumorphin as well as beta-neo-endorphin and dynorphin inhibits the contraction of the rabbit vas deferens which is known to have only the kappa type opiate receptor. This action was also effectively antagonized by Mr2266. It is concluded that leumorphin has potent opioid activity and acts at the kappa receptor, like other opioid peptides derived from preproenkephalin B.