The role of thiosulfate in sulfur metabolism of Rhodopseudomonas globiformis

Rhodopseudomonas globiformis is able to assimilate both sulfur moieties of thiosulfate. During growth on ³⁵S-labelled thiosulfate the amino acids cysteine, homocysteine and methionine were labelled. The bulk of thiosulfate, however, was oxidized to tetrathionate and accumulated in the medium. A thiosulfate: acceptor oxidoreductase was partially purified and characterized. The enzyme oxidized thiosulfate to tetrathionate in the presence of ferricyanide. A c-type cytochrome isolated from this organism was reduced by this enzyme.     

Evidence for intergeneric incompatibility in ferns

The archegonial mucilage ofAthyrium filix-femina andA. distentifolium paralyses spermatozoids ofDryopteris filix-mas (and in one caseD. inaequalis) before they penetrate the archegonial venter. The archegonial mucilage ofDryopteris filix-mas has a weak positive chemotactic influence on the spermatozoids of the twoAthyrium species. The spermatozoids ofDryopteris were never observed in the archegonia ofAthyrium. Incompatibility was not observed within and between the twoAthyrium species, withinDryopteris filix-mas or betweenAthyrium filix-femina and twoAsplenium species.Contribution No. 327.     

Cell differentiation in the absence of intracellular cyclic AMP pulses in Dictyostelium discoideum

Repeated additions of cyclic AMP to a morphogenetic mutant of Dictyostelium discoideum, agip 53, induced cell differentiation to the aggregation competent state as previously reported [Darmon, Brachet, and Pereira da Silva (1975). Proc. Nat. Acad. Sci. USA72, 3163–3166]. Cyclic AMP additions elicited transient increases of the intracellular cyclic GMP concentration but no significant increases of the intracellular cyclic AMP concentration. These results suggest that transient increases of the intracellular cyclic AMP concentration are not necessary for cell differentiation. Agip 53 seems to be unable to relay cyclic AMP signals. A defect in the receptor-mediated activation of adenylate cyclase could be the biochemical basis of the mutant phenotype of agip 53.     

Control of the expression of interleukin-2 activity

Mitogen stimulation of lymphocytes activates phospholipase A₂, which in turn generates arachidonic acid by its action on phospholipids. Cyclooxygenases catalyze the conversion of arachidonic acid to prostaglandins and related cyclic compounds, whereas lipoxygenases direct the formation of straight-chain hydroxylated derivatives such as, for example, the leukotrienes. The studies in this report suggest a correlation between arachidonic acid metabolism and production of the lymphokine, interleukin-2 (IL-2). Inhibitors of phospholipase A₂ activation, mepacrine, tetracaine, glucocorticoids and estradiol, all inhibited the expression of IL-2 activity in concanavalin A-stimulated mouse spleen cells. Inhibition of cyclooxygenase and lipoxygenase activities also resulted in decreased IL-2 production. This was established by the use of the inhibitors 5,8,11,14-eicosatetraynoic acid (ETYA), indomethacin, and nordihydroguajaretic acid (NDGA). A more direct attempt at influencing the arachidonic acid metabolism by addition of the fatty acid to IL-2 production cultures demonstrated that arachidonic acid bound very tightly to IL-2. Extensive dialysis or partial purification of the lymphokine by reverse-phase high-performance liquid chromatography failed to remove the bound arachidonic acid. It was shown, however, that no covalent interactions were involved. In addition to an active arachidonic acid metabolism, continuous protein synthesis was required for expression of IL-2 activity. Thus incubation with puromycin inhibited IL-2 production.     

Semliki forest virus core protein fragmentation: Its possible role in nucleocapsid disassembly

Semliki Forest virus (SFV) envelope proteins function as proton pores under mildly acidic conditions and translocate protons across the viral membrane [Schlegel, A., Omar, A., Jentsch, P., Morell, A. and Kemp, F. C. (1991) Biosci. Rep. 11, 243–255]. As a consequence, during uptake of SFV by cells via receptor-mediated endocytosis the nucleocapsid is supposed to be exposed to protons. In this paper the effects of mildly acidic pH on SFV nucleocapsids were examined. A partial proteolytic fragmentation of core proteins was observed when nucleocapsids were exposed to mildly acidic pH. A similar proteolytic event was detected when intact SFV virions were exposed to identical conditions. Protease protection assays with exogenous bromelain provided evidence that the capsid protein degradation was due to an endogenous proteolytic activity and not to a proteolytic contamination. Detergent solubilization of virus particles containing degraded nucleocapsids followed by sucrose gradient centrifugation led to a separation of capsid protein fragments and remaining nucleocapsids. These data are discussed in terms of a putative biological significance, namely that the core protein fragmentation may play a role in nucleocapsid disassembly.     

Mutation of amino acids within the gibbon ape leukemia virus (GALV) receptor differentially affects feline leukemia virus subgroup B, simian sarcoma-associated virus, and GALV infections.

The three type C retroviruses, gibbon ape leukemia virus (GALV), simian sarcoma-associated virus (SSAV), and feline leukemia virus subgroup B (FeLV-B), infect human cells by interacting with the same cell surface receptor, GLVR1. Using LacZ retroviral pseudotypes and murine cells transfected with mutant GLVR1 expression vectors, we show that the same 9-amino-acid region of human GLVR1 is critical for infection by the three viruses. Rat cells were not susceptible to infection by LacZ (FeLV-B) pseudotypes because of a block at the receptor level. We found multiple amino acid differences from human GLVR1 in the 9-amino-acid critical region of rat GLVR1. Expression of a human-rat chimeric GLVR1 in murine cells demonstrated that rat GLVR1 could function as a receptor for GALV and SSAV but not for FeLV-B. Substitution of human GLVR1 amino acids in the critical region of rat GLVR1 identified three amino acids as responsible for resistance to FeLV-B infection; two of these affect SSAV infection, but none affects GALV infection.     

Expression, Purification, and Characterization of Recombinant Drosophila Choline Acetyltransferase

Abstract: A cDNA for Drosophila choline acetyltransferase (EC 2.3.1.6; ChAT) was fused with a polyhistidine sequence and expressed in Escherichia coli. The recombinant enzyme was purified to a specific activity of 500 μmol/min/mg of protein using metal affinity chromatography and ion exchange chromatography. Kinetic properties of the recombinant enzyme did not differ significantly from those previously determined. Circular dichroism (CD) spectra revealed that the secondary structure of the enzyme is largely μ-helical. Intrinsic fluorescence spectra of the enzyme indicate that its tryptophan residues are buried. Neither CD nor fluorescence spectra changed significantly in the presence of substrates. The cysteine content of the recombinant Drosophila ChAT was determined to be 16 in the absence and 22 in the presence of 6 M guanidine hydrochloride. Finally, crystallization of recombinant Drosophila ChAT was achieved.     

Cloning and characterization of the ALG3 gene of Saccharomyces cerevisiae

The Saccharomyces cerevisiae alg3-1 mutant is descilbed as defectivein the biosynthesis of dolichol-linked oligosaccharides (Huffakerand Robbins, Proc. Natl. Acad. Sci. USA, 80, 7466–7470,1983). Man₅GlcNAc₂-PP-Dol accumulates in alg3 cells and EndoH resistant carbohydrates are transferred to protein by theoligosaccharyltransferase complex. In this study, we describethe cloning of the ALG3 locus by complementation of the temperaturesensitive growth defect of the alg3 stt3 double mutant. Theisolated ALG3 gene complements both the defect in the biosynthesisof lipidlinked oligosaccharides of the alg3-mutant and the underglycosylationof secretory proteins. The inactivation of the nonessentialALG3 gene results in the accumulation of lipid-linked Man₅GlcNAc₂and protein-bound carbohydrates which are completely Endo Hresistant. The ALG3 locus encodes a potential ER-transmembraneprotein of 458 amino acids (53 kDa) with a C-terminal KKXX-retrievalsequence. lipid-linked oligosaccharide N-glycosylation synthetic lethality     

Isolation and rapid sequence characterization of two novel bovine Β-lactoglobulins I and J

Two novel bovineΒ-lactoglobulins I and J have been isolated from bovine milk and characterized by isoelectric focusing. Their primary structure was determined by a very rapid method consisting of a combination of Edman sequencing, mass analysis, and ladder sequencing by mass spectrometry. We found that both newΒ-lactoglobulins are of the bovineΒ-lactoglobulin B-variant type.Β-lactoglobulin I shows Gly instead of Glu at position 108, whereasΒ-lactoglobulin J shows a Pro-to-Leu exchange at position 126.     

No evidence of linkage between the locus for autosomal dominant retinitis pigmentosa and D3S47 (C17) in three Australian families

Summary A linkage analysis has been performed on three Australian families segregating for autosomal dominant retinitis pigmentosa (ADRP). No evidence of linkage has been found in any of the pedigrees studied between the locus D3S47 and the gene for ADRP. The D3S47 locus was found to show very close linkage with the ADRP gene in a large Irish pedigree. Our study together with a similar report on a British family indicates that there is genetic heterogeneity in this disease.