Adhesion ofEnteromorpha swarmers to microbial films

Laboratory experiments were conducted to determine the effect of bacterial films on adhesion ofEnteromorpha sp. reproductive swarmer cells. Swarmers always attached in greater numbers to filmed than to unfilmed polystyrene surfaces. Surface energy measurements produced higher values on filmed surfaces than on unfilmed surfaces. Our data indicate that this higher surface energy may contribute to the increased adhesion by the algal swarmers.     

Functional similarity of HIV-I rev and HTLV-I rex proteins: identification of a new nucleolar-targeting signal in rev protein

We have tested the functional compatibility between rev protein of human immunodeficiency virus type I (HIV-I) and rex protein of human T-cell lymphotropic virus type I (HTLV-I). Each protein recognized the other's cis-acting sequence, albeit at reduced levels. Both proteins localize predominantly in the nucleolus. We have identified a new nucleolar-targeting signal in rev protein, which was homologous to that of rex protein. The sequence [35-RQARRNRRRRWRERQR-50] in rev protein, when fused to the amino-terminus of beta-galactosidase, directed the hybrid protein to the cell nucleolus. A deletion mutant which lacks several amino acid residues within the signal failed to function in the CAT assay system. These results demonstrate that the nucleolar targeting signals are essential for the functions of Rev and Rex.     

Divalent cations regulate glucagon binding. Evidence for actions on receptor-Ns complexes and on receptors uncoupled from Ns

The effects of Mg2+ or ethylenediaminetetraacetic acid (EDTA) on 125I-glucagon binding to rat liver plasma membranes have been characterized. In the absence of guanosine 5'-triphosphate (GTP), maximal binding of 125I-glucagon occurs in the absence of added Mg2+. Addition of EDTA or Mg2+ diminishes binding in a dose-dependent manner. In the presence of GTP, maximal binding occurs in the presence of 2.5 mM Mg2+ (EC50 = 0.3 mM) while EDTA or higher concentrations of Mg2+ diminish binding. Response to exogenous Mg2+ or EDTA depends on the concentration of Mg2+ in the membranes and may vary with the method used for membrane isolation. Solubilized 125I-glucagon-receptor complexes fractionate on gel filtration columns as high molecular weight, GTP-sensitive complexes in which receptors are coupled to regulatory proteins and lower molecular weight, GTP-insensitive complexes in which receptors are not coupled to other components of the adenylyl cyclase system. In the absence of GTP, 40 mM Mg2+ or 5 mM EDTA diminishes receptor affinity for hormone (from KD = 1.2 +/- 0.1 nM to KD = 2.6 +/- 0.3 nM) and the fraction of 125I-glucagon in high molecular weight receptor-Ns complexes without affecting site number (Bmax = 1.8 +/- 0.1 pmol/mg of protein). Thus, while GTP promotes disaggregation of receptor-Ns complexes, Mg2+ or EDTA diminishes the affinity with which these species bind hormone. In the presence of GTP, hormone binds to lower affinity (KD = 9.0 +/- 3.0 nM), low molecular weight receptors uncoupled from Ns.(ABSTRACT TRUNCATED AT 250 WORDS)     

DNA polymerase III holoenzyme of Escherichia coli. II. A novel complex including the gamma subunit essential for processive synthesis

Processive DNA synthesis, a property of DNA polymerase III holoenzyme of Escherichia coli, was not achieved by combining the pol III core (alpha, epsilon, and theta subunits) and the beta and gamma subunits. An activity that restored processivity to these subunits was found in crude extracts and was overproduced 4-fold in cells with plasmids amplifying the tau and gamma subunits. Purified to homogeneity, the activity, assayed by reconstitution of processivity, was represented by five polypeptides which were copurified. Judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, these correspond to the known subunits gamma (52 kDa) and delta (35 kDa) and to three new polypeptides: delta' (33 kDa), chi (15 kDa), and psi (12 kDa). The five polypeptides form a tight complex with a native molecular weight of about 200 kDa and a subunit stoichiometry of two gamma subunits to one each of the others. Processive DNA synthesis, now achieved with only three components (pol III core, beta, and the auxiliary complex), provides the opportunity to assess the functions of each and the contribution that the remaining auxiliary tau subunit makes to reconstitute a holoenzyme.     

FR290581, a novel sordarin derivative: Synthesis and antifungal activity

Sordarin is a unique natural product antifungal agent that is an inhibitor of elongation factor 2. To improve biological activity, we synthesized various compounds by novel modification of the aglycone, sordaricin. As a result, we have discovered the novel sordarin derivative FR290581. This compound exhibited superior activity and a good pharmacokinetic profile, and also displayed good in vivo activity against Candida albicans.     

Synaptic activity prompts γ-secretase–mediated cleavage of EphA4 and dendritic spine formation

Alzheimer''s disease is an age-dependent neurodegenerative disorder that is characterized by a progressive decline in cognitive function. γ-secretase dysfunction is evident in many cases of early onset familial Alzheimer''s disease. However, the mechanism by which γ-secretase dysfunction results in memory loss and neurodegeneration is not fully understood. Here, we demonstrate that γ-secretase is localized at synapses and regulates spine formation. We identify EphA4, one of the Ephrin receptor family members, as a substrate of γ-secretase, and find that EphA4 processing is enhanced by synaptic activity. Moreover, overexpression of EphA4 intracellular domain increases the number of dendritic spines by activating the Rac signaling pathway. These findings reveal a function for EphA4-mediated intracellular signaling in the morphogenesis of dendritic spines and suggest that the processing of EphA4 by γ-secretase affects the pathogenesis of Alzheimer''s disease.     

Possible participation of nonimpulse factors in the increased excitability of partially deafferentated motor neurons

The dynamics of strengthening of monosynaptic segmental response (MSR) in white rats has been studied after bilateral sciatic nerves cuts nearer to the spinal cord (high cut) and farther from it (low cut). 24 hours after the operation the irritation of the posterior root on the side of the high cut stimulates anterior root MSR of authentically larger amplitude than on the side of the low cut and much greater than in intact animals. 48 h, 72 h and 120 h after the operation MSR amplitude on both sides is considerably increased in comparison with the intact animals amplitude but authentically does not differ on the side of the low and high cuts. A connection may be suggested between the excitability increase process of partially deafferented motoneurons with the disturbance of axoplasmatic flow in central sections of the cut afferent fibres.     

The RFC2 gene encoding a subunit of replication factor C of Saccharomyces cerevisiae.

Replication Factor C (RF-C) of Saccharomyces cerevisiae is a complex that consists of several different polypeptides ranging from 120- to 37 kDa (Yoder and Burgers, 1991; Fien and Stillman, 1992), similar to human RF-C. We have isolated a gene, RFC2, that appears to be a component of the yeast RF-C. The RFC2 gene is located on chromosome X of S. cerevisiae and is essential for cell growth. Disruption of the RFC2 gene led to a dumbbell-shaped terminal morphology, common to mutants having a defect in chromosomal DNA replication. The steady-state levels of RFC2 mRNA fluctuated less during the cell cycle than other genes involved in DNA replication. Nucleotide sequence of the gene revealed an open reading frame corresponding to a polypeptide with a calculated Mr of 39,716 and a high degree of amino acid sequence homology to the 37-kDa subunit of human RF-C. Polyclonal antibodies against bacterially expressed Rfc2 protein specifically reduced RF-C activity in the RF-C-dependent reaction catalyzed by yeast DNA polymerase III. Furthermore, the Rfc2 protein was copurified with RF-C activity throughout RF-C purification. These results strongly suggest that the RFC2 gene product is a component of yeast RF-C. The bacterially expressed Rfc2 protein preferentially bound to primed single-strand DNA and weakly to ATP.     

A cationic detergent, cetyltrimethylammonium bromide (CTAB), selectively dissociates the intermediate filament of the fibroblast

We investigated conditions for selective solubilization of the intermediate filament (IF) of BHK-21 cells, and found that a cationic detergent, cetyltrimethylammonium bromide (CTAB), was effective for rapid dissociation of IF into the monomeric form. More selective dissociation was performed with a combination of CTAB and Tween 40. The CTAB-dissociated vimentins were unstable, but the breakdown of them was successfully blocked by leupeptin. Thus, with our extraction buffer, composed of 1% CTAB, 1% Tween 40, 10 mM Tris-HCl (pH 7.4) and 25 micrograms/ml leupeptin, almost all of the vimentin as well as the desmin were solubilized, while two thirds or more of actins were retained in the CTAB/Tween-insoluble fraction.