The amino-terminal domain of rabbit secretory component is responsible for noncovalent binding to immunoglobulin A dimers

Rabbit secretory components (SC) constitute a family of markedly heterogeneous glycoproteins which are released in the secretions as free SC or as SC bound to polymeric immunoglobulins. The aim of this work was to determine the region of the SC polypeptides which is involved in IgA binding. The high and the low Mr forms of free SC (or IgA-dissociated bound SC) and the native secretory IgA complex were subjected to limited tryptic digestion. Chemically characterized peptides ranging in apparent size from 15 to 20 kDa, depending upon the allotype, were shown to be necessary and sufficient for efficient noncovalent binding to IgA dimers (subclass g). These fragments encompass the amino-terminal first domain of SC, i.e. residues 1-126, when aligned with the predicted amino acid sequence from a cDNA clone encoding the rabbit polymeric Ig receptor (Mostov, K.E., Friedlander, M., and Blobel, G. (1984) Nature 308, 37-43). The high and the low Mr forms of SC exhibited the same relative affinity for IgA dimers, suggesting that the postulated internal deletion in the smaller polypeptide (Kühn, L. C., Kocher, H.-P., Hanly, W.C., Cook, L., Jaton, J.-C., and Kraehenbuhl, J.-P. (1983) J. Biol. Chem. 258, 6653-6659) does not impair the IgA dimer recognition function.     

A method for the determination of the electrophoretic patterns of hemolyzed mouse sera

A method is presented that will give comparable results for the evaluation of electrophoretic data on hemolyzed mouse serum patterns. Not only may hemoglobin be determined in the serum, but its contribution to the total protein may be calculated with the aid of a reference curve derived from the data obtained from the hemolyzed red cells of mice taken from the corresponding mouse blood pool.     

An electrophoretic study of the reversible binding of phosphate to ovalbumin.

An electrophoretic method is described for the measurement of relatively weak interaction of ions with proteins, and illustrated with the ovalbumin-phosphate system in 0.1I buffers, pH6.1. Results indicate that under these conditions the interaction of a single dibasic phosphate ion with ovalbumin is described by an association constant of approx. 250M-1.     

An artifactual component of drug-protein binding generated in vitro

In the course of investigating the binding of imipramine to soluble cellular fractions from brain and leukocytes using equilibrium dialysis, an artifactual binding component was produced. On Scatchard and double-reciprocal plots of the data, the component appeared as a homogenous population of sites displaying a binding affinity of 170 nM. The obtained pattern of biphasic interaction bore a marked resemblance to reported Scatchard plots representing the interaction of drugs with bovine serum albumin, and depicting two components of widely differing binding affinity and capacity. The artifact occurred when solutions were transferred after dialysis and before quantitation to intermediate containers, and resulted from binding of 3H-imipramine to the walls of these containers. The latter interaction decreased the concentration of radiolabeled drug in the dialysate but not in the dialyzed solution, and thus mimicked increased imipramine binding to the biological material under study. The effect was particularly pronounced at low drug concentrations, and was particularly pronounced at low drug concentrations, and was prevented by the presence of either proteinaceous material, or of an excess of another basic compound such as methadone. The concentration dependence of the phenomenon led to its appearance as a discrete binding component. The artifact was eliminated either by applying an appropriate correction factor, or by transferring the dialyzed solutions directly into scintillation vials for counting.     

The effects of calcium and magnesium ions on the secondary structure of calcium binding component of troponin

A 40% increase of the α-helicity of calcium binding component of troponin was observed upon addition of micromolar concentrations of calcium ions. Magnesium ions cause also a significan increase of the helical content of this protein but at much higher concentrations than calcium. In the presence of 1mM MgCl₂ micromolar concentrations of calcium ions do not affect the secondary structure of the troponin calcium binding component.     

An electrophoretic component from the lens proteins of the Passeriformes as an important taxonomic characteristic

Zusammenfassung In Agarelektropherogrammen der Linsenextrakte von mehr als 80 untersuchten Passeriformes kommt stets eine charakteristische Komponente vor, welche wir wegen ihrer Regelmäßigkeit, genauen Umgrenzung und besonders stabilen Mobilität Typische Singvogel-Komponente (T S B C) genannt haben.In schwächerer Konzentration ist auch in den Linsenpherogrammen einiger anderer Ordnungen (Ciconiiformes, Falconiformes, Gruiformes, Strigiformes, Psittaciformes, Coraciiformes, Piciformes) eine Fraktion mit ähnlicher Mobilität und ferner fast die ganze Reihe der passeriformen Linsenproteine vorhanden. Weil die Ähnlichkeit zwischen solchen komplizierten Pherogrammen möglicherweise auf eine nähere Verwandtschaft hinweist, hat Verf. eine Übersicht der früheren taxonomischen Argumente, wie sie durch Autoren im Bereich der Anatomie, Osteologie, Myologie, Parasitologie und Biochemie vorgelegt wurden, gegeben und kurz besprochen.     

Macrophage colony stimulating factor (M-CSF) within cord blood sera may be partially responsible for the reduced proliferation of cord blood T cells

We show that there are differences in the soluble factors in cord blood (CB) and adult serum and that these differences play a role in T cell function. Thus, the mitogen and alloantigen-specific proliferative response of adult T cells was enhanced with increasing concentrations of adult serum and CB serum, but to a lesser extent with CB serum. In addition, proliferation of T cells induced by stimulation through the T cell receptor alone (via CD3 stimulation), could be enhanced with adult but not CB serum. However, CB serum enhanced the IL-2-specific proliferative response of pure T cells whereas adult serum did not. To determine whether there was an anti-inflammatory cytokine within CB serum which could induce these results, we assayed our serum samples for anti-inflammatory cytokines. IL-13 could not be detected in any serum sample, whereas IL-10 could be detected in adult but not CB serum (P < 0.002). However, there was a significant difference in the levels of macrophage colony stimulating factor (M-CSF) detected in adult and CB serum samples (P < 0.01). M-CSF was detected in 6/7 CB serum samples (mean +/- SD was 3.8 +/- 2.3 ng/ml) and 0/5 adult serum samples. Furthermore, anti-M-CSF antibody restored the reduced allo-response of T cells incubated in CB serum. Thus, M-CSF may act as a suppressor factor in CB serum. Whether this is sufficient to explain the lack of an allo-response by the foetus to the mother, or the reduced graft-versus-host disease when CB is used instead of bone marrow in stem cell transplantation, is yet to be determined.     

Basic mechanisms responsible for calcium signalling in neuronal cells

Calcium ions are the most universal intracellular messengers transmitting signals from the plasmalemma of excitable cells to the intracellular structures and triggering or modulating in this way most cellular functions. The molecular mechanisms responsible for injection of Ca ions into the cytoplasm during cellular activity and for producting transient elevations of their cytoplasmic free level (calcium “transient,” or “signals”) have been a subject of extensive investigation in numerous laboratories during last three decades. In a short review it is impossible to summarize the results obtained; two extensive publications on this subject have appeared already from our laboratory [1, 2]. Therefore, here the main attention will be paid to the most recent data from our laboratory concerning different aspects of the mechanisms forming calcium signals in neuronal cells.