Globulins composition

From amino acid compositions, evaluations o7" the nutritional potentials of cucurbit meals and globulins can be calculated according to FA0/WH0 (54). The A E ratios, which are the amounts of each essential amino acid relative to the total amount of essential amino acids, are shown in Table II. These data indicate that, like most other oilseeds, cucurbit seeds are deficient in lysine and sulfur-containing amino acids. However, sulfur-containing amino acids are considerably high in CitrullI us colocynthis (egusi, ancestral watermelon) seed protein and exceed the suggested level in FA0/WH0 reference protein (55). 

Discontinuities are seen in the relationship between increase in film pressure, An, and lipid composition following the injection of globulin under monolayers of lecithin-dihydro-ceramide lactoside and lecithin-cholesterol mixtures. The breaks occur at 80 mole % C 16-dihydrocaramide lactoside and 50 mole % cholesterol. Between 0 and 80 mole % lactoside and between 0 and 50 mole % cholesterol the mixed films behave as pure lecithin. Two possible explanations are the formation of complexes, having molar ratios of lecithin-lactoside 1 to 4 and lecithin-cholesterol 1 to 1 and/or the effect of monolayer configurations (surface micelles). In this model, lecithin is at the periphery of the surface micelle and shields the other lipid from interaction with globulin. 

Although glycosphingolipids are the specific lipid components in the antigen-antibody complex, their activity is markedly enhanced by other (auxiliary) lipids such as lecithin and lecithin-cholesterol mixtures (15). The present study deals with the effect of lipid composition on the penetration of lactoside—cholesterol and lactoside—lecithin monolayers by rabbit y-globulin. We also investigated the lecithin-cholesterol system. Furthemore, since criteria for the existence of lipid-lipid complexes in monolayers are still few (8, 17), we have used infrared spectroscopy to examine lipid mixtures for the presence of complexes. 

Figure 2. Effect of lipid composition on surface pressure of films in interaction with rabbit y-globulin at 1 digram/ml.

Film penetration studies show unequivocally that lecithin-cholesterol mixtures containing from 0 to 50 mole % cholesterol and lecithin—lactoside mixtures containing from 0 to 80 mole % Ci6-dihydroceramide lactoside have the same effect as pure lecithin. This suggests the presence of a lipid complex in which lecithin prevents the interaction of the cholesterol or ceramide lactoside with globulin. Over these ranges of composition the lipid film would consist of a mixture of the lecithin-cholesterol or the lecithin-lactoside complex with excess lecithin. One may picture two models in which the protein contact is restricted to molecules of lecithin. In one, individual polar groups of the protein interact with the excess lecithin molecules as well as with the lecithin portions of the complex. In the other model, the protein as a whole interacts with the lecithin sites of polymeric lipid structures. The latter, which could be referred to as surface micelles (I), are visualized also through the term "mono-... 

A model that is consistent with these observations of the action of trypsin and phospholipase A and with the discontinuities in the All-composition curves (Figures 2 and 3) is one in which the lipid monolayer is not a continuous palisade of uniformly oriented lipid molecules but rather an assembly of surface micelles. In this model, proposed by Colacicco (4, 5), the protein first comes into contact with the lipid molecules at the periphery of the surface micelles and then inserts itself as a unit between them. This is the basis for the generalized nonspecific interaction between lipids and proteins which results in increase of surface pressure. One may thus explain the identical All values obtained with films of lecithin and 80 mole % lactoside by picturing the lecithin molecules outside and the lactoside molecules inside the surface micelles. In this model lecithin prevents the bound lactoside from interacting nonspecifically with globulin and produces the same increase in pressure as with a film of pure lecithin. In the mixed micelle the lactose moiety of the lactoside protrudes into the aqueous subphase. Contact of the protein with these or other nonperipheral regions of the surface micelle would not increase the surface pressure. 

The proximate composition of peanut shells and seeds has already been compiled in the earlier review by J. C. Arthur, Jr. The proteins of peanuts were first investigated by Ritthausen in 1880. He extracted the proteins from oil-free peanut cake with sodium chloride and weakly basic solutions and precipitated them by acidification. He considered that the protein thus precipitated was homogeneous but later, Johns and Jones (1916) separated two proteins, arachin and conarachin, by ammonium sulfate fractionation. Afterward, several workers isolated peanut proteins, using different methods, and a survey of methods for separating individual globulins was published by Vanitraub and Shutov (1968). 

Protein Composition of Milk. Skim milk is a colloidal suspension of extreme complexity. The particulate phase, the casein micelles, consists primarily of a mixture of asi, as2, / , and x-caseins combined with calcium ions and an amorphous calcium-phosphate-citrate complex. The soluble phase contains lactose, a fraction of the caseins and calcium, and, in raw milk, the whey proteins, which are predominantly /3-lacto-globulin and a-lactalbumin. When milk is centrifuged at high speed (in our experiments, 30 min at 110,000 X gravity), the casein micelles sediment. This permits one to separate the two physical phases of skim milk and to measure changes in composition of the phases resulting from... 

The remarkable similarity in the molar ratios of the amino acids offers encouragement to the proposition that common peptides will be found in the electrophoretic components of the serum proteins. The peptide of spot 7 probably differs from spot 8 in leucine content, which would account for the higher Rf of spot 8. More encouraging are the recent reports of Edelman (2, 13) who found that gamma-globulin, the Bence-Jones proteins, and the myeloma proteins have a peptide unit of common amino acid composition. 

Thanh and Shibasaki (10) proposed a trimeric structure for the 7S and a hexamerlc structure for the 9S dimer. Urea/sodium dodecyl sulfate polyacrylamide gel electrophoresis resolves the 7S globulin into six isomeric forms which are made up of three types of subunits (a, a and B) in varying proportions (10, 14, 15). The composition of the six isomeric proteins has been designated as follows B.., B, aB2> B, aa B B,, a B ... 

Fig. 2. The dependence of nucleoside-protein conjugation on pH. A mixture of periodate-oxidized adenosine and cytidine was added to bovine y-globulin to give final concentrations of 4 mM nucleoside (0.9 mg/ml) and 6.7 ftM protein (1 mg/ml) in 0.2 M Veronal buffer titrated to varying pH. These mixtures were incubated at room temperature for 1.5 hr. Then sodium borohydride was added to a final concentration of 0.4 M (15 mg/ml), and samples were incubated for 2.5 hr at 4°. They were then dialyzed extensively against 0.1 M NaCl and analyzed for protein and nucleoside composition.

We have attempted to select conditions that minimize the effects of sample compositional differences. The efforts have included using EDTA as part of the assay buffer, using sufficient reaction time, optimizing for maximum sensitivity, which permits dilution of the sample, elevating the concentrations of nonimmune y-globulin and second antibody, and, in some cases, rejecting a specific lot of second antibody. The time required for completion of immunoprecipitation using low concentrations of reactants can require up to a week at 4°. However, use of sufficient concentra-... 

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