Calderon Howe

Erythrocyte membrane proteins: Their study using aqueous pyridine solutions

1. 1. A new method for the study of membrane proteins is described. It involves the use of aqueous pyridine which permits the separation of proteins of human erythrocyte membrane into two fractions: one water soluble and lipid free the other a water-insoluble lipoprotein. Both fractions show multiple bands on gel electrophoresis and the band patterns of the two fractions and the intact membrane are similar. They suggest a close relationship of the proteins of the two fractions in spite of differences in lipid affinity. The sialoglycoprotein, containing the virus receptor activity, is present uniquely in the water-soluble fraction and its isolation is described. 2. 2. The water-soluble proteins show a strong tendency for association. Such aggregation is promoted by certain salts. Aggregates of various sizes are still present in 33% aqueous pyridine and they can be resolved and visualised by gel electrophoresis in 0.1% sodium dodecyl sulfate as outlined by Shapiroet al.22 into about twenty protein bands of a wide range of molecular weights. Certain proteins of the water-soluble fraction are not present as components of these aggregates. They include a sialoglycoprotein and three other proteins which can be visualized as distinct bands on polyacrylamide gels.

Collocalia mucoid: A substrate for myxovirus neuraminidase☆

Abstract A potent inhibitor of myxovirus hemagglutination has been derived by aqueous extraction from the nest-cementing substance (salivary secretions) of the Oriental swiftlet (genus Collocalia ). The active material contains about 50% carbohydrate, is susceptible to the neuraminidase of influenza virus of all strains thus far tested, and lacks detectable blood group antigens. Observations on the relation between viral hemagglutinin, neuraminidase activity, and the conversion of myxoviruses to “indicators” are presented and discussed. Evidence is presented to indicate that the enzymic and hemagglutinative properties of myxovirus may be separate and dissociable functions.

Interaction of polylysine with soluble components of human erythrocyte membranes

Abstract 1. 1. The interactions of poly- l -lysine with soluble erythrocyte components and with Collocalia mucoid, a sialoprotein of avian origin, were studied by electrophoresis and immuno-electrophoresis in agar gel. 2. 2. Polylysine combined with erythrocyte membrane glycoprotein and with Collocalia mucoid to form visible precipitates in agar gel; erythrocyte fractions devoid of glycoprotein failed so to react. 3. 3. A precipitate of virus receptor substance with polylysine could be quantitatively redissolved by the addition of poly- l -aspartic acid to the mixture. Whether this change in solubility occurred as a result of displacement of polylysine from the glycoprotein or by the formation of soluble complexes could not be established. 4. 4. Neuraminidase (EC 3.2.1.18) treatment of erythrocyte glycoproteins and Collocalia mucoid greatly reduced or abolished their capacity to precipitate with polylysine. 5. 5. The findings suggest that N -acetylneuraminic acid in the acid glycoprotein of erythrocyte membranes is an important factor in the agglutination of erythrocytes by polybases, a phenomenon thought to have some bearing on intravascular thrombus formation.

Enzymic Action of Influenza Virus on Human Erythrocyte Stroma Components.

Summary The presence in human erythrocyte stroma of a chromogenic substance giving absorption spectra (direct Ehrlich and Bial reactions) identical with those of crystalline sialic acid has been confirmed. A potent water-soluble inhibitor of viral hemagglutination, containing 7–11% by weight of this chromogen, has been isolated by partition dialysis from concentrated human erythrocyte stroma. 30–40% of the chromogen in the crude stroma concentrate and up to 56% of that in the purified inhibitor was rendered dialyzable following treatment with concentrated infective influenza virus, which in most instances also destroyed receptors for indicator viruses. Limited chromatographic analysis indicated that the dialyzable chromogen is most probably sialic acid. These observations represent the first direct demonstration of split products resulting from enzymic action of influenza virus on human erythrocyte components.

Observations on the relationship between hemagglutinin and neuraminidase of influenza viruses.

Summary A number of mucoids of varying NANA content were found to differ widely in their capacity to inhibit the hemagglutinin of several strains of myxovirus when assayed under standardized conditions. This pattern of inhibition bore no quantitative relationship to the content of NANA of individual mucoids, each of which was found to be susceptible to the neuraminidase of 2 or more strains of active virus. Receptor substance from human and guinea pig erythrocytes inhibited hemagglutination and was susceptible to viral neuraminidase. Stroma and sialic acid-containing receptor-like substances from sheep erythrocytes were neither capable of inhibiting hemagglutination nor susceptible to viral neuraminidase. The implications of these findings are discussed with respect to the separate identities of myxovirus hemagglutinin and enzyme.

Infection-Mediated Resistance to Cell Fusion by Inactive Sendai Virus

Summary The development of resistance to extrinsic fusion by Sendai virus in cells infected with myxoviruses or paramyxoviruses can be attributed to the destruction of sialo-glycoprotein receptors by newly synthesized viral neuraminidase incorporated in the cell membrane and inaccessible to antibody. Infection with any of the viruses which lack neuraminidase does not influence susceptibility to extrinsic fusion by Sendai virus, even though the cell membrane may undergo specific chemical and morphological alterations during viral maturation and release.

The neuraminidase of measles virus.

The agent of measles (rubeola) has been assumed to be a paramyxovirus on the basis of its electron microscopic appearance, its size, its sensitivity to ether and detergents, and the presence of hemagglutinin in the viral envelope. Thus far, however, the one attribute common to myxoviruses, namely neuraminidase, has not been described for measles virus. We have demonstrated that specific neuraminidase activity is associated with measles viral hemagglutinin. The evidence suggests strongly that the enzyme is part of the viral envelope.