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The ganglioside composition of Ehrlich ascites carcinoma (EAC) cells and the role of the individual gangliosides in binding and penetration into the cell of influenza virus were determined. EAC gangliosides identical with or close t o G M~. GMZ, G M~, G T~~ and G T I~ were characterized by thin-layer chromarography, compositional analyses, methylation analysis and mass-spectrometry. The ganglioside uptake capacity of native and neuraminidase-treated EAC cells was studied with tritium-labeled gangliosides of definite structure and the binding of influenza virus to cells was determinated by using ["Hluridine-labeled virus and by heinagglutination studies. Treatment of the cells with Vihrio c l t o l~~r n~~ neuraminidase largely decreased binding of the virus. Exogenous gangliosides with a terminal galactose unit or a penultimate galactose masked by neuraminic acid were able to restore the virus-binding capacity of ncuraminidase-treated cells, however, the main ganglioside of EAC cells, Ghfz, which carbohydrate chain is terminated by N-acetylgalactosamine, was completely ineffective. The common carbohydrate sequence of the gangliosides showing binding activityis proposed to be the main recognition structure of the influenza virus receptor on the surface of EAC cells. Penetration of labeled influenza virus into the nuclei of EAC cells was evaluated by measuring the radioactivity of the nuclei of neuraminidase-treated ganglioside-loaded cells after exposition to the labeled virus. Of all gangliosides tested only trisialogangliosidcs of the G~l b type were able to induce increased entry of the virus into the cells and accumulation of its radioactive component into the nuclei. It is suggested that G T I~ gangliosides react specifically with the virus protein responsible for membrane fusion (apparently the hemagglutinin HA2 subunit) and thus are involved in virus penetration and delivery of the virus genome to the nuclei.When interacting with cells ortho-and paramyxoviruses first adsorb to specific host receptors and then penetrate thc cell. While nothing is known about the nature of the cell surface components involved in the penetration process, some information about the receptors responsible for adsorbtion of the viruses is available. The receptors contain neuraminic acid and their receptor activity is destroyed by neuraminidase [2]. It is therefore thought that glycoproteins [3 -51 or sialoglycolipids (gangliosides) [6 -81 serve as receptors.Comparing the virus-binding activity of glycoproteins isolated from HeLa cells and brain gangliosides, Wu et al.", I showed that adsorbtion of Sendai virus required much less glycoprotein than glycolipid and concluded that the former are responsible for virus attachment. However recently it hdS been demonstrated that di-, tri-and tetrasialogangliosides can function as receptors for Sendai virus in cultured bovine kidney cells [lo, 1 11. Thus, the existing evidence of participitation of gangliosides in virus-cell association is contradictive. Moreover, the data obtained so far d...

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The concentration dependences of the binding of fusicoccins (FCs) A, B, C, D, J and H to plasma membranes isolated from maize (Zea mays L.) roots have been studied in parallel with the effects of these compounds on elongation and (86)Rb transport in detached maize roots. The dissociation constants obtained showed a good correlation between the affinity of the FCs for the plasmalemma and their biological activity. However, the range of physiologically active FC concentrations proved to be about two orders of magnitude higher than that calculated from the dissociation constants. It was also shown that Vicia faba L. mesophyll protoplasts, unlike isolated plasma membranes, have two FC-binding sites, one with a K D similar to that of the isolated plasmalemma while the other has a substantially higher K D , apparently corresponding to the physiologically active state of the FC-binding proteins.