Organization of centromeres in the decondensed nuclei of mature human sperm

The localization of centromeres in mature human sperm was shown by immunofluorescent labeling and nonisotopic in situ hybridization. In the decondensed nucleus structural elements (dimers, tetramers, linear arrays and V shape structures) formed by individual centromeres of nonhomologous chromosomes were observed. They organize the compact chromocenter, which was shown for nuclei decondensed to a low extent. The chromocenter is buried inside the nucleus; in contrast, telomeric regions of chromosomes were tentatively localized on the periphery. Thus, a gross architecture, which can influence selective unpackaging of the paternal genome upon fertilization, exists in human sperm.     

Culture performance of different strains and crosses of the European sea bass (Dicentrarchus labrax) reared under controlled conditions at Eilat, Israel

The European sea bass (Dicentrarchus labrax) is one of the most important commercial marine fish species in the Mediterranean basin. However, broodstock domestication and selective breeding on a production scale have yet to be exploited. We reared progeny of sea bass from three different strains and their crosses throughout the entire growth cycle to market size. Data sets were analyzed to assess whether culture performance differs among different strains and crosses reared under controlled laboratory conditions using both separate and communal rearing techniques. Strains and crosses of sea bass varied significantly for traits of economic interest such as growth, survival, body composition, sex ratio, sexual maturation patterns of males, and frequencies of body shape abnormalities. Lack of evidence for substantial heterosis for growth among reciprocal crosses was also detected. Significant sexual dimorphism for length and weight was evident in all strains and crosses. At market size, the resulting weight advantages of females varied between strains and crosses; overall average weight advantage for females was about 39%. Length and weight of individual fish were strongly correlated during different time intervals. This may be useful for the choice of selection criteria, raising the possibility that the response to selection for weight at market time may be achieved by conducting selection on young fish. Generally, the results showed a high culture potential of sea bass strains originating from the southeastern areas of the Mediterranean Sea, suggesting that these domesticated strains can be exploited in future selective breeding programs.     

The X-ray structure of human serum ceruloplasmin at 3.1 Å: nature of the copper centres

The X-ray structure of human serum ceruloplasmin has been solved at a resolution of 3.1?Å. The structure reveals that the molecule is comprised of six plastocyanin-type domains arranged in a triangular array. There are six copper atoms; three form a trinuclear cluster sited at the interface of domains 1 and 6, and there are three mononuclear sites in domains 2, 4 and 6. Each of the mononuclear coppers is coordinated to a cysteine and two histidine residues, and those in domains 4 and 6 also coordinate to a methionine residue; in domain 2, the methionine is replaced by a leucine residue which may form van der Waals type contacts with the copper. The trinuclear centre and the mononuclear copper in domain 6 form a cluster essentially the same as that found in ascorbate oxidase, strongly suggesting an oxidase role for ceruloplasmin in the plasma.     

Stability of α-chymotrypsin conjugated with poly (ethylene glycols) and proxanols at high temperature and in watercosolvent mixtures

Summary -Chymotrypsin has been modified with poly(ethylene glycols) and proxanols, block-copolymers of poly(propylene oxide) and poly(ethylene oxide). These conjugates were several-fold more thermostable and showed high catalytic activity at elevated concentrations of water-miscible organic cosolvents (alcohols and dimethyl sulfoxide) which caused inactivation of free (non-modified) -chymotrypsin.     

Protein exporter function and in vitro ATPase activity are correlated in ABC-domain mutants of HlyB

The Escherichia coli toxin exporter HlyB comprises an integral membrane domain fused to a cytoplasmic domain of the ATP-binding casette (ABC) super-family, and it directs translocation of the 110kDa haemolysin protein out of the bacterial cell without using an N-terminal secretion signal peptide. We have exploited the ability to purify the soluble HlyB ABC domain as a fusion with glutathione S-transferase to obtain a direct correlation of the in vivo export of protein by HlyB with the degree of ATP binding and hydrolysis measured in vitro. Mutations in residues that are invariant or highly conserved in the ATP-binding fold and glycine-rich linker peptide of prokaryotic and eukaryotic ABC transporters caused a complete less of both HlyB exporter function and ATPase activity in proteins still able to bind ATP effectively and undergo ATP-induced conformational change. Mutation of less-conserved residues caused reduced export and ATP hydrolysis, but not ATP binding, whereas substitutions of poorly conserved residues did not impair activity either in vivo or in vitro. The data show that protein export by HlyB has an absolute requirement for the hydrolysis of ATP bound by its cytoplasmic domain and indicate that comparable mutations that disable other prokaryotic and eukaryotic ABC transporters also cause a specific loss of enzymatic activity.     

Studies of lipopolysaccharides from Yersinia pseudotuberculosis subtypes VA and VB

Lipopolysaccharides (LPS) from various strains of Yersinia pseudotuberculosis type V have been isolated and characterised. Differences in sugar composition and serological activity of LPS from various strains within the same subtype of Y. pseudotuberculosis have been revealed.     

Purification and properties of the RuvA and RuvB proteins of Escherichia coli

Summary The RuvA and RuvB proteins of Escherichia coli play important roles in the post-replicational repair of damaged DNA, genetic recombination and cell division. In this paper, we describe the construction of over expression vectors for RuvA and RuvB and detail simple purification schemes for each protein. The purified 22 kDa RuvA polypeptide forms a tetrameric protein (M_r ca. 100000) as observed by gel filtration. The tetramer is stabilised by strong disulphide bridges that resist denaturation during SDS-PAGE (in the absence of boiling and -mercaptoethanol). In contrast, purified RuvB polypeptides (37 kDa) weakly associate to form a dimeric protein (M_r ca. 85000). At low protein concentrations, the RuvB dimer dissociates into monomers. The multimeric forms of each protein may be covalently linked by the bifunctional cross-linking reagent dimethyl suberimidate. Addition of purified RuvA and RuvB to a RecA-mediated recombination reaction was found to stimulate the rate of strand exchange leading to the rapid formation of heteroduplex DNA.     

Microtubule and Actin Interplay Drive Intracellular c-Src Trafficking

The proto-oncogene c-Src is involved in a variety of signaling processes. Therefore, c-Src spatiotemporal localization is critical for interaction with downstream targets. However, the mechanisms regulating this localization have remained elusive. Previous studies have shown that c-Src trafficking is a microtubule-dependent process that facilitates c-Src turnover in neuronal growth cones. As such, microtubule depolymerization lead to the inhibition of c-Src recycling. Alternatively, c-Src trafficking was also shown to be regulated by RhoB-dependent actin polymerization. Our results show that c-Src vesicles primarily exhibit microtubule-dependent trafficking; however, microtubule depolymerization does not inhibit vesicle movement. Instead, vesicular movement becomes both faster and less directional. This movement was associated with actin polymerization directly at c-Src vesicle membranes. Interestingly, it has been shown previously that c-Src delivery is an actin polymerization-dependent process that relies on small GTPase RhoB at c-Src vesicles. In agreement with this finding, microtubule depolymerization induced significant activation of RhoB, together with actin comet tail formation. These effects occurred downstream of GTP-exchange factor, GEF-H1, which was released from depolymerizing MTs. Accordingly, GEF-H1 activity was necessary for actin comet tail formation at the Src vesicles. Our results indicate that regulation of c-Src trafficking requires both microtubules and actin polymerization, and that GEF-H1 coordinates c-Src trafficking, acting as a molecular switch between these two mechanisms.     

Protoplast fragmentation as one of the possible mechanisms of L-transformation of bacteria (Clostridium perfringens)]

As revealed, the action of lysozyme on the cells of Clostridium perfringens BP-6K led to the formation of not only typical spheroplasts, but also of cells whose peripheral parts of the cytoplasm were fragmented by membrane component. Small bodies framed by the membrane proper and containing granular and fibrillar components were formed. They were polymorphic in osmium treatment, and had smooth contours in preliminary use of aldehyde fixation. In the latter case a dense lumpy material analogous to the one which fills the periplasmic zone and serves as a rigid wall component formed at the surface of the protoplasm and bodies-fragments. In case of escape of the bodies into the external environment through the perforations in the cell wall the principal mass of the protoplast remains intact. The morphology of the bodies-fragments indicated a principal possibility of their autonomic existence. It is supposed that the phenomenon described could serve as one of the mechanisms of L-cell formation.