the extractability of inner-membrane proteins from salmonella typhimurium intact cells, spheroplasts and inner-membrane fragments by non-denaturing detergents

the effect of triton x-100, na cholate and tween 80 on the solubilization of integral membrane proteins in intact cells, spheroplasts and inner-membrane fragments of salmonella typhimurium was studied. the detergents were used in various concentrations (1.6 to 64 mm) and cytochromes b and d were used as marker to monitor the solubilization of membrane-bound proteins. results showed that no inner-membrane protein solubilization was detected after the treatment of intact cells with detergents. the effect of na cholate and tween 80 on spheroplasts and inner-membrane fragments was also negligible in comparison to triton x-100. triton x-100 solubilized cytochromes from inner-membrane fragments more efficiently than from spheroplasts. the ratio of total protein solubilization to solubilize cytochromes showed that in spheroplasts this ratio was maximum at 1.6 mm triton x-100 while it was maximum at 16-32 mm triton x-100 in inner-membrane fragments. this difference between spheroplasts and inner-membrane fragments may be due to the orientation of the inner- membrane in spheroplasts (right side out) and inner-membrane fragments (in-side out as well as right side out), and to the presence of peripheral proteins attached to cytoplasmic membrane in spheroplasts