The amino acid sequence of low-potential cytochrome c550 from the cyanobacterium Microcystis aeruginosa

The low-potential cytochrome c550 has been purified from the cyanobacterium Microcystis aeruginosa and its amino acid sequence has been determined. The protein contains 135 amino acid residues with the Cys-X-X-Cys-His heme binding site at residues 37 to 41. The sequence from residue 28 to 45 shows similarity to cytochrome c553 residues 1 to 18 when the heme binding sites are aligned. Another region of similarity is in the carboxyl-terminal regions of these two proteins. The two aligning regions of cytochrome c553 correspond to helical segments in other related cytochromes. A partial sequence of cytochrome c550 from Aphanizomenon flos-aquae was obtained and showed a 48% identity to the sequence of the M. aeruginosa cytochrome. The single methionine residue in cytochrome c550 of M. aeruginosa occurs at position 119 but there is no methionine in this region in the A. flos-aquae cytochrome, indicating that methionine is not the sixth ligand to the heme iron atom. Histidine 92 is a possible sixth ligand in M. aeruginosa cytochrome c550. The far-uv circular dichroism spectrum indicates that this protein is approximately 17% alpha helix, 42% beta-pleated sheet, and 41% random coil.     

Nematode infestation of fillets from Atlantic cod, Gadus morhua, off eastern Canada

The prevalence and intensity of larval nematodes in fillets of Atlantic cod, Gadus morhua, were examined and compared with similar data from a previous survey conducted about 30 yr ago. Anisakis simplex occurred more often in the nape of the fillet, whereas Pseudoterranova decipiens was the predominant species in napeless fillets. The results suggest an increase in both the prevalence and intensity of P. decipiens in fillets of cod, especially those originating from the Gulf of St. Lawrence and coastal Nova Scotia.     

Effects of mot gene expression on the structure of the flagellar motor

Direct freezing procedures have enabled us to visualize distinctive intramembrane particle ring structures in the cytoplasmic membranes of peritrichously flagellated bacteria by means of freeze-fracture electron microscopy. These structures were identified as flagellar motor components because their distribution matched that of flagella, and because they were absent in non-flagellated mutants of Escherichia coli. Particle rings were present in both the Gram-positive Streptococcus and the Gram-negative E. coli. In E. coli, a non-functional mocha operon produced flagellated but immotile cells lacking the particle rings. Simultaneous introduction of the motA and motB genes, led to recovery of both motility and the ring structures but neither gene alone was sufficient. The concomitant loss of the rings and motility is consistent with the ring particles having a central role in the flagellar motor.     

A study on the cytoplasmic granules of the pericardial gland cells of some bivalve molluscs

The pericardial glands of three bivalve molluscs are composed of convoluted epithelium that appears as pouches on the auricles of Mytilus and as tubules in the connective tissue at the anterior-lateral sides of the pericardial cavity of Mercenaria and Anodonta. The pericardial gland cells are attached to each other by many randomly placed desmosome-like cell junctions and gap junctions. Belt-desmosomes that are characteristic of epithelial cells were not observed. The basal membrane of these cells is invaginated producing complex interdigitating cytoplasmic processes and filtration slits. The pericardial gland cells stain for the presence of iron with Prussian blue stain. Electron-dense and electron-lucent granules of various diameters are present in the cytoplasm. Many electron-dense granules contain ferritin-like particles in which the presence of iron has been demonstrated by microanalysis. It is suggested that these particles are the iron storage protein ferritin since they contain iron, and are water soluble, heat stable, and morphologically similar to mammalian ferritin. Ferritin particles are probably both synthesized and broken down by the pericardial gland cells; thus the pericardial gland cells may be involved in iron homeostasis in these molluscs.     

Neurosecretion of the mediodorsal cells of the central nervous system of the snail Helisoma duryi

Summary The neurosecretory mediodorsal cells that produce a putative growth hormone of the snail Helisoma duryi were studied in fast-growing virgin snails and in slow-growing reproducing snails. There are about 60 mediodorsal cells in clusters on each side of the cerebral commissure of the central nervous system, and they contain dense-cored granules which are 100–200 nm in diameter. The cells of virgin snails have dense Golgi bodies, scattered ER cisternae, and few granules, while those of reproducing snails have pale Golgi bodies, stacked ER cisternae, and numerous granules. Thus the mediodorsal cells of the virgin snails appear to be more active synthetically than those of the reproducing snails. The cells near the endocrine dorsal bodies contain many dorsal body precesses in their membrane interdigitations. There are junction-like interactions between some of the interdigitations. Gap junction-like contacts are seen between mediodorsal cells and glial cells. The axon endings of the mediodorsal cells at the neurohemal area in the labial nerve show more release profiles in virgin snails than in reproducing snails. A daily pattern of release has been observed in reproducing snails, and rates of release are higher in the evening than in the morning.     

Design of liposome to improve encapsulation efficiency of gelonin and its effect on immunoreactivity and ribosome inactivating property

Gelonin, purified from the seeds of Gelonium multiflorum, using cation-exchange and gel-filtration chromatography was characterised for its purity, homogeneity and molecular weight by reverse-phase HPLC (RP-HPLC) and SDS-PAGE analysis. The HPLC purified gelonin was used for entrapment studies in the liposomes. Liposomes were prepared by reverse phase evaporation (REV) technique using three different types of lipid composition in the same molar ratio. The method resulted in 75–80% entrapment efficiency of gelonin in the liposomes. Entrapped and unentrapped gelonin was characterized for physico-chemical, immunochemical and biological properties. The immunoreactivity of entrapped gelonin was fully preserved but the ribosome-inactivating property was slightly inhibited. The method involved mild conditions, highly reproducible and the liposomes produced appeared to be stable for several months. It has important implications in the development of cell type specific cytotoxic agents where a chemical cross-linking is involved which significantly inhibits both immunoreactivity and ribosome-inactivating ability of the toxin.     

Chemical and enzymatic incorporation of N2-(p-n-butylphenyl)-2''-deoxyguanosine into an oligodeoxyribonucleotide.

An 18mer oligodeoxyribonucleotide containing a N2-(p-n-butylphenyl)-2'-deoxyguanosine (BuPdG) residue at the 3' end has been synthesized by both chemical and enzymatic methods. Chemical synthesis involved attachment of 5'-DMT-BuPdG as the 3'-H-phosphonate to uridine-controlled pore glass (CPG), followed by extension via H-phosphonate chemistry. After oxidation of the backbone, deprotection of bases, and removal from CPG, the uridine residue was removed by periodate cleavage and beta-elimination. The resulting oligomer 3'-phosphate was digested with alkaline phosphatase to give the free BuPdG-18mer. E.coli DNA polymerase I (Klenow) incorporated BuPdGTP at the 3' end of the corresponding 17mer primer annealed to a complementary 29mer template, and the properties of this product were identical to those of chemically synthesized BuPdG-18mer. E.coli DNA polymerase I (Klenow) was unable to extend the BuPdG-18mer, and the 3' to 5' exonuclease activity of the enzyme was unable to remove the modified nucleotide.