Immunological analysis of the structural molecules of erythrocyte membrane in mice. I. Analysis of the aqueous phase molecules obtained by butanol fractionation of erythrocyte membrane

Solubilization of SV40 plasma-membrane-associated large tumor antigen using single-phase concentrations of 1-butanol

The nature of the interaction of the simian virus 40 (SV40) transforming protein, large tumor antigen (T-ag), with the plasma membrane of transformed cells is not well understood. We report here that SV40 plasma-membrane-associated large tumor antigen (pmT-ag) can be solubilized by using single-phase concentrations of 1-butanol. Purified plasma membranes from SV40-transformed mouse cells yielded T-ag when treated with 2.5% butanol; solubilization of T-ag from the purified membranes in butanol was temperature dependent, with approximately 10-fold more T-ag extracted at 37 degrees C than at 22 degrees C; and application of 2.5% butanol to mKSA cells after cellular surface proteins had been radiolabeled with 125I resulted in the release of iodinated T-ag. Butanol-extracted pmT-ag coprecipitated with p53 and several cellular proteins ranging in size from 35 to 60 kDa. One cellular component migrated at a mobility similar to that of tubulin (56 kDa), and a monoclonal antibody against the alpha subunit of tubulin coprecipitated T-ag. Immunoblotting of proteins immunoprecipitated with monoclonal antibodies against T-ag or p53 from butanol extracts with a monoclonal antibody against the beta subunit of tubulin revealed specific coprecipitation of tubulin with T-ag and p53. This suggests that complexes composed of tubulin, T-ag, and p53 exist in butanol extracts. Control experiments eliminated the possibility of an artifactual association of tubulin with T-ag and p53 induced by butanol. Two-dimensional gel analyses revealed that 2.5% butanol at 37 degrees C extracted a subset of membrane-associated proteins and some cytosolic proteins, as well as a number of proteins that were not soluble in either high salt or detergent. Thus, the butanol extraction conditions employed in this study recovered a species of pmT-ag that appears to complex with tubulin. As butanol reportedly is less deleterious to native protein structures than other agents, including high salts and detergents, this extraction procedure may be useful for studying the structure and function of other membrane-associated proteins.

Selective extraction by 1-butanol of surface glycoprotein antigens from human melanoma cells

The butanol extraction method has previously been used to achieve selective release of tumor-specific transplantation antigens from mouse sarcoma cells. In this study we investigated the feasibility of this method for extracting four surface glycoprotein antigens (87K, 95-150K, HLA-DR, and HLA-A,B,C) from cultured human melanoma cells. Of the four antigens examined, only 95-150K and HLA-DR antigens could readily be detected in material extracted by 2%, 3%, or 5% butanol. The 3% butanol was found to be most effective in releasing these two antigens. Treatment of melanoma cells with less than or equal to 3% butanol did not decrease the viability of extracted cells as judged by either Trypan Blue dye exclusion or plating efficiency. Thus the noncytolytic butanol extraction method offers a promising approach to the isolation of certain glycoproteins such as 95-150K and HLA-DR from viable human melanoma cells for further purification and structural analysis.

Biosynthesis of mouse erythrocyte membrane proteins by Friend erythroleukemia cells

The synthesis of mouse erythrocyte membrane proteins by Friend erythroleukemia cells during dimethyl sulfoxide-induced differentiation was studied. Untreated and dimethyl sulfoxide-treated cells were incubated with L-[3H]leucine and the incorporation of radioactivity into total trichloroacetic acid-insoluble proteins and into proteins immunoprecipitated with a multivalent rabbit antibody to mouse erythrocyte membranes was determined. The immunoprecipitated membrane proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis and radioactivity was detected by fluorography. The incorporation of L-[3H]leucine into total cell proteins was linear for 20 min in both untreated and treated cells. Exposure of the cells to dimethyl sulfoxide had an inhibitory effect on protein synthesis, with a significant decrease noted on the fourth day of treatment and a continued decline occurring until the seventh day when protein synthesis was 42% that of untreated cells. The synthesis of erythrocyte membrane proteins was 0.49% that of total cell proteins in untreated cells, was increased to 1.27% by the third day of treatment and remained at about 1% of total protein synthesis from the fourth to the seventh day. Untreated cells synthesized low levels of spectrin, bands 5 and 6 proteins. Treatment with dimethyl sulfoxide caused a staggered increase in synthesis of a number of erythrocyte membrane proteins. Spectrin synthesis increased 4-fold by the third day of treatment and declined thereafter. The synthesis of membrane proteins with electrophoretic mobilities similar to bands 3 and 4 was increased 2--3-fold by the fourth day, while bands 6 and 5 proteins attained maximal synthesis (4-fold) on the fifth and sixth days of treatment.

The use of denaturing conditions for gel diffusion of insoluble epidermal proteins

Modifications of the classical technique for double diffusion in agar plates are presented. These procedures allow insoluble proteins to be dissolved in a variety of denaturing solvents and antibody production specificity to be monitored by the appearance of precipitin lines in agarose gels as in the conventional Ouchterlony method. Results obtained using the insoluble proteins of bovine epidermis are summarized.

Immunological analysis of Mycoplasma membranes

The antigens responsible for the production of antibodies to Mycoplasma laidlawii and M. gallisepticum causing growth and metabolic inhibition of these organisms were localized in the cell membrane. Various membrane fractions were tested for serological activity. Membrane lipids were completely or almost completely inactive, whereas several preparations of defatted membrane proteins retained some serological activity, shown by their ability to stimulate metabolic inhibition antibody in rabbits and to adsorb metabolic inhibition antibody and form precipitation lines with an antiserum to the membrane. When the membranes were heated to 65 C for 1 hr, they virtually lost their ability to adsorb metabolic inhibition antibody, which suggests that the antigenic determinants are proteins. Serological activity was retained in reaggregated membranes obtained by dialysis against Mg(2+) of membranes solubilized in sodium dodecyl sulfate. The amount of solubilized membrane protein and lipid incorporated into the reaggregated membranes could be regulated by varying the Mg(2+) concentration. As the serological tests indicated that the various membrane antigens were selectively incorporated into the different reaggregated membranes, the use of controlled reaggregation of solubilized membranes is suggested as a new tool for the fractionation and antigenic analysis of membrane proteins.