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Biomedical subjects

E M Kosower

Publications and source records attributed to E M Kosower.

At least 37 records · Page 2Linked to original sources
PubMed1983

Selection of ion channel elements in the serine and aspartate methyl-accepting chemotaxis proteins of bacteria.

Two plausible, transmembrane ion channel elements (These 'elements' are alpha-helical sequences of 24 amino acids in which polar, hydrophilic side chains occupy one side and hydrophobic side chains the other) have been identified in the serine chemoreceptor-methyl-accepting chemotaxis protein (MCP) (SerR) of E. coli and the aspartate chemoreceptor-MCP (AspR) of S. typhimurium. That the chemoreceptor might serve as, or activate, an ion channel is supported strongly by the occurrence of membrane depolarization, specific peptide methylation and neurotoxin inhibition of response in the chemotaxis of S. aurantia (E.P. Greenberg, refs. 13-18).

Amino Acid Sequence↗
PubMed1983

Partial tertiary structure assignments for the beta-, gamma- and delta-subunits of the acetylcholine receptor on the basis of the hydrophobicity of amino acid sequences and channel location using single group rotation theory.

Four transmembrane segments from each of the beta-, gamma- and delta-protein subunits of the acetylcholine receptor (AChR) [Nature (1983) 301, 251-255], [Proc. Natl. Acad. Sci. USA (1983) 80, 1111-1115] have been selected on the basis of single group rotation (SGR) theory [Symp. Structure and Dynamics of Nucleic Acids and Proteins (Sept. 1982) abst. pp. 52-53], [Biochem. Biophys. Res. Commun. (1983) 111, 1022-1029] and the hydrophobicity of amino acid sequences. One helix from each subunit is assigned to the AChR ion channel. Criteria for the selection of ion channel elements are outlined.

Amino Acid Sequence↗
PubMed1983

Membrane-mobility agent-promoted fusion of erythrocytes: fusibility is correlated with attack by calcium-activated cytoplasmic proteases on membrane proteins.

Rat, but not human, erythrocytes undergo fusion promoted by the membrane-mobility agent 2-(2-methoxyethoxy)-ethyl cis-8-(2-octylcyclopropyl)octanoate (A2C). The difference in behavior is correlated with rat erythrocyte membrane protein degradation caused by Ca2+-activated proteases. The human erythrocyte is deficient in such protease activity. Membrane protein degradation is a necessary, but not sufficient, requirement for membrane fusion. Membrane protein degradation probably releases membrane components from certain constraints. In addition, the motion of membrane components precedes fusion and must be promoted by reagents such as A2C, leading to the creation of fusion-potent lipid areas. This sequence of chemical and physical events occurs in other fusion processes.

Animals↗
PubMed1981

Dynamic changes of red cell membrane thiol groups followed by bimane fluorescent labeling.

Monobromobimane labels red cell membrane protein thiol groups; bands exhibit fluorescence after sodium dodecyl sulfate acrylamide gel electrophoresis and correspond to almost all of those staining with Coomassie blue. The response of membrane protein thiol groups to oxidative challenge and the dynamics of recovery of the thiol groups may be followed. Diminished labeling is found after oxidation with diamide, with both intrachain and interchain disulfide bond formation demonstrated by sodium dodecyl sulfate acrylamide gel electrophoresis. Regeneration of thiol groups under physiological conditions (incubation with glucose) after a moderate degree of diamide oxidation is shown to be complete (with respect to thiol group content and degree and distribution of bimane label) in normal human red blood cell membranes. Even after oxidation of almost half of the membrane protein thio groups (maximum degree of oxidation achieved), regeneration of thiol groups is almost complete; a minor fraction resides in the form of disulfide-linked high molecular weight proteins (demonstrated by the electrophoretic profile) which may be reduced completely with dithiothreitol. Bimane fluorescent labeling provides a convenient and sensitive method for following membrane thiol group status under physiological conditions.

Bridged Bicyclo Compounds↗
PubMed1981

Cell membrane receptor classes delimited through cap formation either with diamide or with membrane mobility agent, A2C.

Receptors on normal human peripheral blood lymphocytes can be divided into two classes by means of the capping response exhibited in the presence of the reagents, diamide or colchicine (microtubule-related) and A2C (microtubule-independent). Diamide and colchicine promote capping of concanavalin A (Con A) receptors. Diamide capping is reversible, while colchicine capping is not reversible under the conditions used. A2C does not promote the capping of Con A receptors. In contrast, diamide and colchicine do not affect the rate at which either anti-immunoglobulin (anti-Ig) or wheat germ agglutinin (WGA) receptors cap, but A2C effectively enhances cap formation for both anti-Ig and WGA receptors. The simplicity of the classification method promises to be of use in the investigation of membrane receptors.

Azo Compounds↗
PubMed1980

Membrane fusion induced by the membrane mobility agent, A2C. Differentiation between fusible and non-fusible cells. Transfer of fusibility.

Red cells of different species respond differently to the treatment with the membrane mobility agent, A2C, with respect to both the A2C interaction and the subsequent cell-cell interaction. Depending on whether both, one or neither of the processes are effective, some red cells (e.g., nucleated Leghorn hen red cells, rat red cells) fuse easily, some (human red cells) show morphological changes but do not fuse, and others (nucleated Rock hen red cells) show little or no response. Mixed fusion (i.e., between fusible cells of different species) is readily obtained, indicating that no species-specific recognition sites are required for A2C-induced fusion. the potential for fusion is a transferable characteristic. In the presence of fusible cells, A2C induces both heterologous and homologous fusion of otherwise 'non-fusible' cells. Electron micrographs of fusing cells after treatment with A2C reveal 'onion-ring' structures ('whorls'), free of intramembranous protein particles but different from the smooth appearance of A(2)C particles. Whorls are considered to arise from fusion-potent membrane areas. Fusion is apparent at multiple sites along the contact line between apposed membranes. The postulated appearance of vesicle-like structures along the fusion line (Kosower, E.M., Kosower, N.S. and Wegman, P. (1977) Biochim. Biophys. Acta 471, 311-329) is confirmed by micrographs. The mechanism of this fusion process is duscussed and compared to other types of fusion process.

Animals↗
PubMed1980

Bimane fluorescent labels. Characterization of the bimane labeling of human hemoglobin.

The products of the bimane labeling (using a monobromobimane, a dibromobimane and a quaternary bromobimane) of hemoglobin are characterized. Peptide mapping identifies cysteine-beta 93 as the reactive thiol site. Electrophoretic mobility of hemoglobin varies with the label used, that of monobromobimane-labeled hemoglobin being unaltered, while dibromobimane- and trimethylammoniobromobimane-labeled hemoglobin exhibit changes. The oxygen affinity of labeled hemoglobin is changed from that of hemoglobin. Deoxyhemoglobin is substantially less reactive towards monobromobimane than oxyhemoglobin. Bimane-labeled hemoglobin is more easily denatured on heating than unlabeled hemoglobin. Possible uses for bimane labels in the study of protein properties are pointed out. Bimane labeling agents are derivatives of 3,4,6,7-tetramethyl-1,5-diazabicyclo[3.3.0]-octa-3,6-diene-2,8-dione 9,10-dioxa-syn-(methyl,methyl)bimane).

Aza Compounds↗
PubMed1979

Bimane fluorescent labels: labeling of normal human red cells under physiological conditions.

The bimane fluorescent labels, monobromobimane, dibromobimane, and monobromotrimethylammoniobimane, are derivatives of syn-9,10-dioxabimane:1,5-diazabicyclo[3.3.0]octa-3,6-diene-2,8-dione. They efficiently label hemoglobin (reactive thiol groups), membrane proteins, and glutathione of normal human red cells under physiological conditions. Monobromobimane and dibromobimane are effective on intact cells while red cell membranes may be impermeable to the positively charged monobromotrimethylammoniobimane, the latter being effective only on lysed cells. These bimane labels provide a class of labeling agents that may have wide applicability in biological materials.

Aza Compounds↗
PubMed1978

F20C, a new fluorescent membrane probe, moves more slowly in malignant and mitogen-transformed cell membranes than in normal cell membranes.

New fluorescent probes of membrane mobility can be introduced into cell membranes at single points with particles of a membrane mobility agent, A2C. The initial entry of fluorescence from the particle into the cell membrane and the subsequent lateral spread of fluorescence have been observed for cells in suspension. A dramatic difference between the behavior of normal lymphocytes and that of mitogen-transformed and mastocytoma cells is found. Both the initial entry and the spreading of fluorescence are much slower in the transformed and tumor cells than in the normal cells at 18 degrees C. Entry and spread of fluorescence in normal cells become slow enough to be observed only at 12 degrees C or below.

Cell Line↗