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PubMed1976

Crosslinking with bifunctional reagents as a means for studying the symmetry of oligomeric proteins.

A method based upon the principle that unlike domains of bonding are reflected in different reactivities and distribution of residues that can be crosslinked, has been elaborated for the determination of symmetry of oligomeric proteins. The derivation of theoretical curves for the prediction of crosslinking patterns of tetramers produced by reaction with a bifunctional reagent and subsequent sodium-dodecylsulphage-gel electrophoretic analysis, is presented. Based upon the theory the symmetry properties of a tetramer, to the extent whether it is an isologous or heterologous association, can be deduced by a simple calculation. Crosslinking patterns obtained with rabbit muscle aldolase and pig muscle lactate dehydrogenase after treatment with a series of diimidoesters of increasing chain length are evaluated and shown to be consistent with the expectations for isologous tetramers. From the patterns obtained with the various reagents the distances between lysyl residues located nearest to each other in different subunits in the two proteins could also be determined.

Actins↗
PubMed1978

Oligomeric immunoglobulin A antibody response to rubella virus infection.

Pooled sera from rubella patients in the early convalescent stage, containing a high titer of hemagglutination-inhibiting (HI) antibody, were treated with protein A-conjugated gel to reduce immunoglobulin G (IgG) antibody and then centrifuged in sucrose gradients. This treatment resulted in the detection of an HI activity peak sedimenting at a rate intermediate between 7S and 19S. In contrast to the 19S antibody, the HI activity of this peak was not abolished by 2-mercaptoethanol, but sedimented at 7S after this treatment. The activity was considered to consist of IgA oligomers, since it was removed by anti-IgA immunosorbent. The appearance of the oligomeric IgA antibody after the infection was then studied using serum samples collected sequentially from five rubella patients. Shortly after the onset of the disease, the HI activity appeared at high titer and thereafter gradually decreased in titer until it could no longer be detected in the sera. The time of its disappearance varied with each patient.

Antibodies, Viral↗
PubMedDate not supplied

[Mathematical model of electrogenic transport through biomembranes via oligomeric channels capable of conformational transitions].

A mathematical model of electrogenic ion transport across biomembranes by oligomeric channels liable to conformational transformations has been derived. The model describes changes with time of the membrane potential and near--membrane ion concentrations. Different types of the channel conductance regulation such as activation or inhibition by the permeating ions and membrane potential have been considered. It appears that in the presence of such regulations 1) the channel voltage-current curves have negative resistance regions; 2) the dependence of the quasisteady state (or resting) potential on the ion concentrations in the solution is of hysteresis nature; 3) the model may have multiple steady-state and oscillating solutions.

Cell Membrane Permeability↗
PubMed1976

Oligomeric structure of A1 arginase from rat liver and A4 from kidney. Difference in charge of subunits.

1. The predominant form of rat liver arginase, A1, and that of kidney, A4, were isolated and partially purified. 2. It was found that arginase A4, similarly as A1, has oligomeric structure. Either of the enzymes on EDTA treatment dissociates into inactive subunits of molecular weight 30 000 daltons. Addition of Mn2+ ions restores the activity and causes reassociation of subunits to the native form of 120 000 mol. wt. 3. The subunits of A4 differ considerably in electrophoretic mobility from subunits of A4, which probably is the reason why the native forms of the enzyme from kidney and liver differ in electrophoretic behaviour.

Animals↗
PubMed1979

Geometry of the dry-state oligomerization of 2',3'-cyclic phosphates.

Evaporation of a solution of thymidine plus either the exo or the endo diastereomer of uridine cyclic 2',3'-O, O-phosphorothioate (U greater than p(S) in 1,2-diaminoethane hydrochloride buffer gave the 2',5' and 3',5' isomers of (P-thio) uridylylthymidine (Up(S)dT) in a ratio of 1:2 with a combined yield of about 20%. These isomers were re-converted to U greater than p(S) and dT by a reaction that is known to proceed by an in-line mechanism. Both the 2',5' and 3',5' isomers gave as product the same diasteromer of U greater than p(S) that had been used originally in their formation. These dry-state 'prebiotic' reactions (Verlander, Lohrmann, and Orgel 1973) are thus shown to be stereospecific, and both the 2',5' and 3',5' internucleotide bonds are formed by an in-line mechanism.

Chemical Phenomena↗
PubMed1977

Two Escherichia coli fructose-6-phosphate kinases. Preparative purification, oligomeric structure and immunological studies.

Two isoenzymes of fructose-6-phosphate kinase (ATP: D-fructose-6-phosphate 1-phosphotransferase, EC 2.7.1.11) are present in Escherichia coli K12. One isoenzyme is allosterically inhibited by phosphoenolpyruvate and activated by nucleoside diphosphates, and is a tetramer composed of four subunits of molecular weight 35 000. A simple method for the purification of this enzyme is reported. Equilibrium dialysis indicates that there are four ATP sites and four GDP sites per tetramer. The second isoenzyme is present in low quantity in wild type bacteria. This enzyme is devoid of allosteric properties. A complete method of purification is described. Determination of its molecular weight under native and denaturing conditions indicates that this protein is a dimer composed of two subunits of molecular weight 36 000. Antisera have been produced against both isoenzymes. The antiserum against one isoenzyme does not cross-react with the other. Discrepancies between our results and those of other workers are discussed.

Allosteric Regulation↗
PubMed1975

Beta-D-xylosidase from Bacillus pumilus. Molecular properties and oligomeric structure.

Bacillus pumilus beta-D-xylosidase, purified by affinity chromatography, seems to be homogeneous, as judged by disc electrophoresis and gel filtration. The absorption coefficient at 280 nm, Ao, 1% 1cm, determined by the dry weight method, is 1.78. The complete amino acid composition is determined. Sedimentation velocity studies show the presence of two components with S20, W values of 10.0 S and 6.6 S. After glutaraldehyde cross-linking two, enzymically active, components, with apparent molecular weights 126 000 and 243 000, can be isolated by preparative sucrose gradient ultracentrifugation. These values are confirmed by analytical disc electrophoresis at different acrylamide concentrations. The subunit molecular weight is 60 000. L-Methionine is the only N-terminal amino acid detectable. The possible presence of both dimeric and tetrameric forms of the beta-D-xylosidase in solution has to be envisaged.

Amino Acids↗