Phosphoproteins in dictyostelium discoideum

The phosphoproteins of Dictyostelium discoideum were compared at different stages of development by polyacrylamide gel electrophoresis. Certain phosphoproteins of vegetative amoebae were conserved while others appeared and disappeared during development. Four major phosphoproteins with apparent subunit molecular weights of 50,000, 47,000, 38,000, and 34,000 disappeared precociously in response to exogenous cAMP. Two membranal phosphoproteins, with apparent subunit molecular weights of 80,000 and 81,000, appeared precociously in response to added cAMP. One of these phosphoproteins, molecular weight of 80,000, has been identified tentatively as the “contact site A” glycoprotein. Another membranal protein, with apparent subunit molecular weight of 42,000, unaffected in its appearance by cAMP, has been identified tentatively as phosphoactin.     

Spontaneous Aggregation and Cytotoxicity of the β-Amyloid Aβ1–40: A Kinetic Model

The time dependency of the spontaneous aggregation of the fibrillogenic β-Amyloid peptide, Aβ^1–40, was measured by turbidity, circular dichroism, HPLC, and fluorescence polarization. The results by all methods were comparable and they were most consistent with a kinetic model where the peptide first slowly forms an activated monomeric derivative (AM), which is the only species able to initiate, by tetramerization, the formation of linear aggregates. The anti-Aβ antibody 6E10, raised against residues 1–17, at concentrations of 200–300 nM delayed significantly the aggregation of 50 μM amyloid peptide. The anti–Aβ antibody 4G8, raised against residues 17–24, was much less active in that respect, while the antibody A162, raised against the C-terminal residues 39–43 of the full-length Aβ was totally inactive at those concentrations. Concomitant with the aggregation experiments, we also measured the time dependency of the Aβ^1–40–induced toxicity toward SH-EP1 cells and hippocampal neurons, evaluated by SYTOX Green fluorescence, lactate dehydrogenase release, and activation of caspases. The extent of cell damage measured by all methods reached a maximum at the same time and this maximum coincided with that of the concentration of AM. According to the kinetic scheme, the latter is the only transient peptide species whose concentration passes through a maximum. Thus, it appears that the toxic species of Aβ^1–40 is most likely the same transient activated monomer that is responsible for the nucleation of fibril formation. These conclusions should provide a structural basis for understanding the toxicity of Aβ^1–40 in vitro and possibly in vivo.     

Internal lipid synthesis and vesicle growth as a step toward self-reproduction of the minimal cell

One of the major properties of the semi-synthetic minimal cell, as a model for early living cells, is the ability to self-reproduce itself, and the reproduction of the boundary layer or vesicle compartment is part of this process. A minimal bio-molecular mechanism based on the activity of one single enzyme, the FAS-B (Fatty Acid Synthase) Type I enzyme from Brevibacterium ammoniagenes, is encapsulated in 1-palmitoyl-2oleoyl-sn-glycero-3-phosphatidylcholine (POPC) liposomes to control lipid synthesis. Consequently molecules of palmitic acid released from the FAS catalysis, within the internal lumen, move toward the membrane compartment and become incorporated into the phospholipid bilayer. As a result the vesicle membranes change in lipid composition and liposome growth can be monitored. Here we report the first experiments showing vesicles growth by catalysis of one enzyme only that produces cell boundary from within. This is the prototype of the simplest autopoietic minimal cell.     

Identifying essential genes in bacterial metabolic networks with machine learning methods

Background  

Identifying essential genes in bacteria supports to identify potential drug targets and an understanding of minimal requirements for a synthetic cell. However, experimentally assaying the essentiality of their coding genes is resource intensive and not feasible for all bacterial organisms, in particular if they are infective.     

DISTANCE DATA REVISITED

Abstract— Objections to my earlier demonstration, that the branch lengths of trees fitted to distance matrices have no physical interpretation, are shown to be ill-founded. In particular the contention of Felsenstein, that fitted lengths estimate expectations of amounts of change, is shown to lead to a paradox. A method is introduced for constructing multiple trees of optimal or near-optimal fit to distance data, and this is found to give better performance than previous methods. Most published trees based on distances have been poorly chosen. Consensus trees of several trees with near-optimal fit are found to be quite poorly resolved, and it appears that molecular distances seldom provide much useful information on phylogenetic relationships.     

Evidence for essential primary amino groups in a bacterial coupling factor F1ATPase

We have found that the binding of pyridoxal-5′-phosphate to 6 primary amino groups leads to the inactivation of the enzyme. A preferential reaction of pyridoxal-5′-phosphate with the α-subunits of this enzyme can be demonstrated. The reactivity of the amino groups is influenced by various effectors. In the presence of ATP the inhibition of the ATPase activity is noncompetitive.     

Trees on networks: resolving statistical patterns of phylogenetic similarities among interacting proteins

Background  

Phylogenies capture the evolutionary ancestry linking extant species. Correlations and similarities among a set of species are mediated by and need to be understood in terms of the phylogenic tree. In a similar way it has been argued that biological networks also induce correlations among sets of interacting genes or their protein products.     

Multiple polyadenylation sites in a Drosophila tropomyosin gene are used to generate functional mRNAs.

The gene encoding muscle tropomyosin I in Drosophila is alternatively spliced in embryonic and thoracic muscle to generate two sizes classes of RNAs. By Northern blot analysis, the embryonic RNA class shows a broad RNA band of hybridization of 1.3 kb and a more sharply defined, less abundant RNA band at 1.6 kb. The thoracic class of RNAs, on the other hand, consists of a broad hybridization band at 1.7 kb and a more sharply defined band at 1.9 kb. Each size class of RNA encodes a different tropomyosin isoform. The two classes of alternatively spliced RNAs utilize the same 3' terminal exon of the gene. The DNA sequence of this exon reveals a cluster of several polyadenylation signals (AAUAAA) or polyadenylation-like signals. We show here by S1 nuclease protection analysis that at least five and possibly seven of these polyadenylation or polyadenylation-like sequences are associated with in vivo embryonic and thoracic mRNA cleavage processing sites. Six of these S1 sites are clustered within 119 bp and a seventh is located 255 bp downstream. At least one of the polyadenylation-like signal sequences appears to be an unusual AACAAA sequence. In addition we also show that these mRNAs function in vitro to synthesize muscle tropomyosins.     

Antibodies to the hepatitis A virus in the healthy population of Moscow

Serum specimens collected from 1002 persons in Moscow were tested for the presence of antibodies to hepatitis A virus (anti-HAV antibodies) by solid-phase enzyme immunoassay. The prevalence of these antibodies increased progressively with age from 10% in children aged 5-9 years to over 90% in the age groups of 40-49 years and over, the 50% immunity level being established at the age of 18 years. 79% of infants under 1 year were found to be immune, which was obviously due to the placental transfer of antibodies from mother to child. In a considerable part of seropositive persons over 30 years high or medium antibody titers were detected. These age groups showed a stable proportion of the low, medium and high level of anti-HAV antibodies. The prevalence of such antibodies was not related to sex. The presence of an ample amount of anti-HAV antibodies was determined in all of 18 tested lots of commercial serum immunoglobulin obtained from 3 different manufacturers.     

Vegetative fallows and potential value of the neem tree (Azadirachta indica) in the tropics

Research into the systems of agriculture based on vegetative fallows should begin from enquiries into the shrubs and trees most efficient in restoring soil productivity and providing firewood, timber, fodder and other products essential to meeting basic needs at the rural household and community level. Local processing of such products can give rise to the establishment of thriving village industries and thus generate employment and additional income. Neem tree,Azadirachta indica, of the semiarid regions is one outstanding example of a species which is not only an efficient soil ameliorant but can also provide a series of products highly competitive in price and quality with petroleum-based synthetics. Enough scientific evidence has been gathered from several hundred references on the subject to warrant the launching of a well coordinated multidisciplinary research and development programme leading to agricultural, industrial and commercial exploitation of this tree. Proposals for the implementation of several projects within the programme are briefly outlined in this paper.