Effects of acetic acid on growth and fermentative activity of Saccharomyces cerevisiae

The effect of acetic acid on the growth and the fermentative activity of S. cerevisiae was analysed comparatively with the pH. This study showed that the pH does not affect these two activities. On the contrary, the acetic acid has an inhibition effect. This effect was modelised by the relation of Levenspiel. Finally, it was shown that the quantities of acetic acid produced by Brettanomyces were not sufficient to explain the inhibition of Saccharomyces.     

Comparative analyses of human immunodeficiency virus type 1 (HIV-1) and HIV-2 Vif mutants.

Virion infectivity factor (vif), a gene found in all lentiviruses, plays an essential role in virus replication in certain target cells. We examined the replication competence of the human immunodeficiency virus type 2 (HIV-2) vif mutant in different T-cell lines and primary cells in comparison with that of the HIV-1 vif mutant. Both mutant viruses were unable to replicate in peripheral blood-derived mononuclear cells but replicated with wild-type efficiency in certain T-cell lines, such as SupT1 and MOLT-4/8. These results confirm the importance of vif in the infection of relevant target cells and imply that some cellular factor(s) could compensate for vif function. However, HIV-1 and HIV-2 vif mutant viruses also show differential replications in other cell lines, suggesting either different threshold requirements for the same cellular factor(s) or the involvement of different factors to compensate for vif-1 and vif-2 functions. By cross complementation experiments, we showed that vif-1 and vif-2 have similar functions. Our studies further indicate the existence of two kinds of nonpermissive cells: H9 is unable to complement HIV-1 delta vif but is susceptible to a one-round infection with HIV-1 delta vif produced from permissive cells. In contrast, U937 is nonpermissive for HIV-2 delta vif produced from permissive cells but, once infected, is able to complement the delta vif function. In both types of nonpermissive cells, a step prior to proviral DNA synthesis is affected.     

Amphotericin B derivative blocks human immunodeficiency virus type 1 entry after CD4 binding: effect on virus-cell fusion but not on cell-cell fusion.

The antiviral effect of MS8209, an amphotericin B derivative, was studied in CD4+ cells transfected with a lacZ gene inducible upon human immunodeficiency virus type 1 (HIV-1) infection. MS8209 was shown to block virus entry after receptor binding and probably before virus-cell membrane fusion, but it had no effect on syncytium formation, although both processes are mediated by HIV-1 envelope proteins and CD4.     

Cloning,characterization and overproduction of nuclease S1 gene (nucS) from Aspergillus oryzae

The nuclease S1 gene (nucS) from Aspergillus oryzae was isolated using a polymerase-chain-reaction-amplified DNA fragment as a probe, and a 2.6-kb SalI-EcoRI fragment containing the nucS gene was sequenced. It was deduced that the nucS gene had two short introns, 49 and 50 nucleotides in lenght. The nucS gene had an open-reading frame of 963 base pairs and coded for a protein of 287 amino acid residues, comprising the signal peptide of 20 amino acids and a mature protein of 267 amino acids. The deduced amino acid sequence agreed well with the published amino acid sequence except for one substitution. Southern hybridization analysis showed that the nucS gene existed as a single copy in the A. oryzae chromosome. When the structural gene of nucS was fused with the promoter of the glaA gene and introduced into A. oryzae, the yield od secreted nuclease S1 increased about 100-fold compared with the recipient strain.     

Accumulation of a novel spliceosomal complex on pre-mRNAs containing branch site mutations.

Pre-mRNA assembles into spliceosomal complexes in the stepwise pathway E-->A-->B-->C. We show that mutations in the metazoan branchpoint sequence (BPS) have no apparent effect on E complex formation but block the assembly of the A complex and the UV cross-linking of U2 small nuclear ribonucleoprotein particle (snRNP) proteins. Unexpectedly, a novel complex, designated E*, assembles on pre-mRNAs containing BPS mutations. Unlike the E complex, the E* complex accumulates in the presence of ATP. U1 snRNP and U2AF, which are tightly bound to pre-mRNA in the E complex, are not tightly bound in the E* complex. Significantly, previous work showed that U1 snRNP and U2AF become destabilized from pre-mRNA after E complex assembly on normal pre-mRNAs. Thus, our data are consistent with a model in which there are two steps in the transition from the E complex to the A complex (E-->E*-->A). In the first step, U1 snRNP and U2AF are destabilized in an ATP-dependent, BPS-independent reaction. In the second step, the stable binding of U2 snRNP occurs in a BPS-dependent reaction.     

Macrophage colony-stimulating factor induces thrombospondin I production by cultured human macrophages

The role of colony-stimulating factors (CSFs) in regulating the synthesis of thrombospondin 1 (TSP1) by cultured human macrophages is investigated. Macrophage (M)-CSF is shown rapidly and transiently to induce two predominant species of TSP1 mRNA. One of these species was 3.2 kb in size and appeared to be specific to M-CSF-stimulated macrophages. Adherent M-CSF-treated macrophages are also shown to express abundant surface cell-associated TSP rapidly when examined by indirect immunofluorescence staining. Granulocyte-macrophage (GM)-CSF induced TSP1 mRNA at a later time point, and this was attributable to the effects of endogenous M-CSF induced by the GM-CSF; the GM-CSF-treated cells did not display surface-associated TSP after 3 hr of treatment. Analysis of the TSP1 protein synthesised by the M-CSF-treated macrophages revealed the expected trimeric form of the molecule. In addition, an unidentified 95-kDa protein was found to be covalently associated with immunoreactive TSP1, and this appeared to be specific to the macrophages as it was not found in TSP1 precipitated from other cell types. It is suggested that the induction of TSP1 by M-CSF may play an important role in the major physiological functions of macrophages. © 1995 Wiley-Liss, Inc.     

Design of metal ion binding peptides

Two cyclic and branched peptides (PLA and AZU) were synthesized with the aim of reproducing the active site of the blue copper proteins plastocyanin and azurin. Both peptides, designed on the basis of the x-ray structures of Poplar plastocyanin and Alcaligenes denitrificans azurin. contain the same coordinating residues of the parent native proteins. The visible spectra of PLA in the presence of equimolar amount of Cu(II) strongly support the interaction between the peptide and copper(II) ion. The CD titration of AZU with the Hg(II) ion indicates for the formation of two species. [A ZUHg]⁺ and [A ZUHg₂]³⁺ having binding constants (K_eq) of 3.10⁶ and 2–10⁴M^?1, respectively. © 1994 John Wiley & Sons, Inc.     

Parametric sensitivity of stoichiometric flux balance models applied to wild-type Escherichia coli metabolism

The esterification of lauric acid with geraniol catalyzed by the commercially immobilized lipase preparation from Mucor miehei, Lipozyme(R), was studied in well-stirred flasks. The enzyme support was characterized in terms of its internal and external surface area, protein location, and protein content. It was found that the enzyme was mainly located on the external surface of the support, therefore, internal diffusional limitations were not important. It was also shown that the protein content of the support depends on the size of the particle, with smaller particles containing higher amounts of protein per unit weight. Under the conditions studied, the reaction was not under external mass transfer limitations, and the initial reaction rate depended on the size of the support particles. This was mainly due to the different protein contents on the support as a function of particle size and not to internal or external mass transfer limitations. Also, it was found that the inhibition exerted by water was predominantly a physical effect due to its accumulation around the enzyme. It was also found that the reaction was substrate inhibited by lauric acid, but not by geraniol. (c) 1995 John Wiley & Sons, Inc.