Characterization of the myoplasma membrane proteins: III. Gel filtration and immunological characterization of Acholeplasma laidlawii membrane proteins

Abstract

Acholeplasma laidlawii (formerly Mycoplasma laidlawii) membranes solubilized by ionic and nonionic detergents were fractionated on Sephadex G-200 columns containing the detergent used for solubilization. When sodium dodecyl sulfate or sodium deoxycholate were present, membrane lipids were resolved as a single elution peak while membrane proteins formed several reproducible peaks. Gel filtration in the presence of the nonionic detergents Triton X-100, Brij 58 and Lubrol W was usually inferior. The proteins were eluted as two broad peaks, one of which included the void volume. Since the NADH oxidase, ATPase and p- nitrophenylphosphatase activities of the solubilized membranes could be detected in the first peak, containing little or no lipid, it appears that these enzymes do not depend on membrane lipids for activity. Serological activity could be demonstrated in membrane fractions isolated by gel filtration, even when sodium dodecyl sulfate was used. However, the use of deoxycholate enabled the separation of a membrane protein fraction highly enriched in antigens which elicited the production of antibodies inhibiting A. laidlawii metabolism and growth. A high content of antigens located on the outer membrane surface was evidenced by the high agglutination titer of A. laidlawii cells exhibited by antisera to this fraction.