Chromosome translocations in wild populations of tetraploid emmer wheat in Israel and Turkey

Translocation frequencies (as compared to the standard chromosome arrangement typified by that in Chinese Spring) in 9 or more genotypes from each of 15 populations of Triticum dicoccoides in Israel were determined. Data also were obtained from 2 genotypes of the southernmost population (Jaba). A single population from Turkey was also investigated. There were 119 genotypes with translocations in the sample of 171 genotypes investigated (70%). The frequency of translocations in different populations varied from 0.27 to 1.00, and all populations had 1 or more genotypes with one or more translocations. Some populations such as Qazrin appeared to be homogeneous for translocations, but most populations were heterogeneous. A sample of 17 genotypes from 12 of the populations were crossed with the Langdon D-genome disomic substitutions to determine the identity of the chromosomes involved in the translocations. There were nine genotypes with translocations and with the exception of a 2A/2B translocation, none of them involved the same chromosomes. The B-genome chromosomes were involved in translocations more frequently than the A-genome chromosomes. Translocation frequencies (TF) of the various populations were correlated with environmental variables, primarily with water availability and humidity, and possibly also with soil type. In general, TF was higher in peripheral populations in the ecologically heterogeneous frontiers of species distribution than in the central populations located in the catchment area of the upper Jordan valley.     

Effects of large Saduria entomon (Isopoda) on spatial distribution of their small S. entomon and Monoporeia affinis (Amphipoda) prey

We performed laboratory experiments to investigate the effects of predator avoidance and numerical effects of predation on spatial distribution of small Saduria entomon (Isopoda) and Monoporeia affinis (Amphipoda), with large S. entomon as predators. The horizontal distribution and mortality of the prey species, separately and together, were studied in aquaria with a spatial horizontal refuge. We also estimated effects of refuge on mortality of small S. entomon and M. affinis by experiments without the refuge net. In addition, we investigated whether predation risk from large S. entomon influenced the swimming activity of M. affinis, to clarify the mechanisms behind the spatial distribution. Both small S. entomon and M. affinis avoided large S. entomon. The avoidance behaviour of M. fffinis contributed about 10 times more to the high proportion in the refuge than numerical effects of predation. Due to the low mortality of small S. entomon the avoidance behaviour of this species was even more important for the spatial distribution. The combined effect of avoidance behaviour and predation in both species was aggregation, producting a positive correlation between the species in density. M. affinis showed two types of avoidance behaviour. In the activity experiments they reduced activity by 36% and buried themselves in the sediment. In the refuge experiments we also observed avoidance behaviour with the emigration rate from the predator compartment being twice the immigration rate. The refuge did not lower predation mortality in M. affinis, probably due to the small scale of the experimental units in relation to the mobility of the species. Predation mortality in small S. entomon was higher in absence of a refuge and especially high in absence of M. affinis.     

Protein 1a: A major wheat germ agglutinin binding protein on the surface of human granulocytes associated with the cytoskeleton

Lectin-receptors on leukocyte and endothelial surfaces are becoming more important in the light of increasing evidence which implicates lectin-carbohydrate interactions in diverse physiological phenomena. This study reports the identification of a major 118 kDa granulocyte surface protein, (Protein 1a) which binds the lectin wheat germ agglutinin (WGA), and is distinctly different from reported WGA binding granulocyte membrane proteins. Protein 1a has been isolated from the Triton-soluble and Triton-insoluble lysates of normal individuals and patients with Chronic Myeloid Leukemia (CML) using a combination of differential solubilization, lectin affinity, ion exchange chromatography and HPLC. The protein from the detergent lysates of both normal and CML granulocytes has similar pI values, lectin affinities, and hydrophobicity. However, its solubility in Triton is different in the two cell types. In 71% of CML cases examined, Protein 1a exhibits decreased Triton solubility suggesting its increased association with the cytoskeleton (CSK). Stimulation of normal granulocytes with WGA leads to the translocation of the soluble form of Protein 1a to the Triton-insoluble fraction. This cytoskeletal recruitment of Protein 1a is sustained only under conditions of excess WGA and occupied receptor. The CSK disruptive agent dihydrocytochalasin B (H₂CB) releases the insoluble form of the receptor into the Triton-soluble fraction. Investigation of a CSK-involving process such as ligand internalization revealed that CML granulocytes exhibit slower kinetics of internalization of fluorescent WGA molecules. Since Protein 1a is a major WGA receptor on the granulocyte surface, its decreased Triton solubility in CML granulocytes suggests that this may be one of the factors contributing to the defective receptor-mediated endocytosis of WGA by CML cells, arising as a consequence of altered membrane-CSK interaction — a nodal point in the signal transduction cascade.     

Characterization of the Palmitoylation Domain of SNAP-25

Abstract: SNAP-25 (synaptosomal associated protein of 25 kDa) is a neural specific protein that has been implicated in the synaptic vesicle docking and fusion process. It is tightly associated with membranes, and it is one of the major palmitoylated proteins found in neurons. The functional role of palmitoylation for SNAP-25 is unclear. In this report, we show that the palmitate of SNAP-25 is rapidly turned over in PC12 cells, with a half-life of ∼3 h, and the half-life for the protein is 8 h. Mutation of Cys to Ser at positions 85, 88, 90, and 92 reduced the palmitoylation to 9, 21, 42, and 35% of the wild-type protein, respectively. Additional mutations of either Cys^85,88 or Cys^90,92 nearly abolished palmitoylation of the protein. A similar effect on membrane binding for the mutant SNAP-25 was observed, which correlated with the degree of palmitoylation. These results suggest that all four Cys residues are involved in palmitoylation and that membrane association of SNAP-25 may be regulated through dynamic palmitoylation.     

The Human Obesity Gene Map: The 1996 Update

An update of the human obesity gene map up to October 1996 is presented. Evidence from Mendelian disorders exhibiting obesity as a clinical feature, single-gene mutation rodent models, quantitative trait loci uncovered in crossbreeding experiments with mouse, rat, and pig models, association and case-control studies with candidate genes, and linkage studies with genes and other markers is reviewed. All chromosomal locations of the animal loci are converted into human genome locations based on syntenic relationships between the genomes. A complete listing of all these loci reveals that only 4 of the 24 human chromosomes are not yet represented, i.e., 9, 18, 21, and Y. Several chromosome arms are characterized by the presence of several putative loci. The following arms include at least three such loci: 1p, 1q, 3p, 4q, 6p, 7q, 8p, 8q, 11p, 11q, 15q, 20q, and Xq. Studies with negative association and linkage results are also reviewed.     

Chromatin arrangements in intact interphase nuclei examined by laser confocal microscopy

Using a laser confocal microscope, chromatin arrangements in intact interphase nuclei were investigated in four plant species. Chromosomes in these plants have specific segments that can be stained with the fluorescent dye chromomycin A₃ (CMA). We stained centromeres inHordeum vulgare, sub-telomeric regions inSecale cereale, satellites inChrysanthemum multicore, and the satellites and the short arms of chromosomes with satellites inHemerocallis middendorfii. The following points were shown: (1) In mitotic interphase nuclei, the centromere and the telomeres of both arms touched the nuclear membrane and had evident polarity. Some CMA-bodies in sub-telomeric regions do not contact the nuclear membrane. (2) Differentiated nuclei had a non-random construction. Polarity of chromosomes is maintained, however, the chromosomes are far apart from the nuclear membrane. (3) Associations in sub-telomeric regions in the interphase nuclei ofSecale cereale were probably due to the association of heterochromatic regions with identical repeated sequences rather than telomere associlations. (4) In interphase nuclei ofChrysanthemum multicore, satellites fused during interphase.     

Water molecules participate in proteinase-inhibitor interactions: crystal structures of Leu18, Ala18, and Gly18 variants of turkey ovomucoid inhibitor third domain complexed with Streptomyces griseus proteinase B.

Crystal structures of the complexes of Streptomyces griseus proteinase B (SGPB) with three P1 variants of turkey ovomucoid inhibitor third domain (OMTKY3), Leu18, Ala18, and Gly18, have been determined and refined to high resolution. Comparisons among these structures and of each with native, uncomplexed SGPB reveal that each complex features a unique solvent structure in the S1 binding pocket. The number and relative positions of water molecules bound in the S1 binding pocket vary according to the size of the side chain of the P1 residue. Water molecules in the S1 binding pocket of SGPB are redistributed in response to the complex formation, probably to optimize hydrogen bonds between the enzyme and the inhibitor. There are extensive water-mediated hydrogen bonds in the interfaces of the complexes. In all complexes, Asn 36 of OMTKY3 participates in forming hydrogen bonds, via water molecules, with residues lining the S1 binding pocket of SGPB. For a homologous series of aliphatic straight side chains, Gly18, Ala18, Abu18, Ape18, and Ahp18 variants, the binding free energy is a linear function of the hydrophobic surface area buried in the interface of the corresponding complexes. The resulting constant of proportionality is 34.1 cal mol-1 A-2. These structures confirm that the binding of OMTKY3 to the preformed S1 pocket in SGPB involves no substantial structural disturbances that commonly occur in the site-directed mutagenesis studies of interior residues in other proteins, thus providing one of the most reliable assessments of the contribution of the hydrophobic effect to protein-complex stability.     

Characterization of a quaternary-structured folding intermediate of an antibody Fab-fragment.

Antibody folding is a complex process comprising folding and association reactions. Although it is usually difficult to characterize kinetic folding intermediates, in the case of the antibody Fab fragment, domain-domain interactions lead to a rate-limiting step of folding, thus accumulating folding intermediates at a late step of folding. Here, we analyzed a late folding intermediate of the Fab fragment of the monoclonal antibody MAK 33 from mouse (kappa/IgG1). As a strategy for accumulation of this intermediate we used partial denaturation of the native Fab by guanidinium chloride. This denaturation intermediate, which can be populated to about 90%, is indistinguishable from a late-folding intermediate with respect to denaturation and renaturation kinetics. The spectroscopic analysis reveals a native-like secondary structure of this intermediate with aromatic side chains only slightly more solvent exposed than in the native state. The respective partner domains are weekly associated. From these data we conclude that the intramolecular association of the two chains during folding, with all domains in a native-like structure, follows a two-step mechanism. In this mechanism, presumably hydrophobic interactions are followed by rearrangements leading to the exact complementarity of the contact sites of the respective domains.     

Biogenesis of mitochondria: Defective yeast H+-ATPase assembled in the absence of mitochondrial protein synthesis is membrane associated

We have investigated the extent to which the assembly of the cytoplasmically synthesized subunits of the H⁺-ATPase can proceed in a mtDNA-less (rho°) strain of yeast, which is not capable of mitochondrial protein synthesis. Three of the membrane sector proteins of the yeast H⁺-ATPase are synthesized in the mitochondria, and it is important to determine whether the presence of these subunits is essential for the assembly of the imported subunits to the inner mitochondrial membrane. A monoclonal antibody against the cytoplasmically synthesized -subunit of the H⁺-ATPase was used to immunoprecipitate the assembled subunits of the enzyme complex. Our results indicate that the imported subunits of the H⁺-ATPase can be assembled in this mutant, into a defective complex which could be shown to be associated with the mitochondrial membrane by the analysis of the Arrhenius kinetics of the mutant mitochondrial ATPase activity.This paper is No. 61 in the seriesBiogenesis of Mitochondria. For paper No. 60, see Novitskiet al. (1984).     

Non-aceticlastic methanogenesis from acetate: acetate oxidation by a thermophilic syntrophic coculture

Methanogenesis from acetate by a rod-shaped enrichment culture grown at 60° C was found to require the presence of two organisms rather than a single aceticlastic methanogen. A thermophilic Methanobacterium which grew on H₂/CO₂ or formate was isolated from the enrichment. Lawns of this methanogen were used to co-isolate an acetate oxidizer in roll tubes containing acetate agar. The rod-shaped acetate oxidizer was morphologically distinct from the methanogen and did not show F₄₂₀ autofluorescence. The coculture completely degraded 40 mol/ml acetate, and produced nearly equal quantities of methane, and methanogenesis was coupled with growth. The doubling time for the coculture at 60°C was 30–40 h and the yield was 2.7±0.3 g dry wt/mol CH₄. Studies with ¹⁴C-labelled substrates showed that the methyl group and the carboxyl group of acetate were both converted primarily to CO₂ by the coculture and that CO₂ was concurrently reduced to CH₄. During growth, there was significant isotopic exchange between CO₂ and acetate, especially with thecarboxyl position of acetate. These results support a mechanism for methanogenesis from acetate by the coculture in which acetate was oxidized to CO₂ and H₂ by one organism, while H₂ was subsequently used by a second organism to reduce CO₂ to CH₄. Since the H₂ partial pressure must be maintained below 10^-4 atm by the methanogen for acetate oxidation to be thermodynamically feasible, this is an example of obligate interspecies hydrogen transfer. This mechanism was originally proposed for a single organism by Barker in 1936.