[Distribution of Na+, K+-ATPase and Mg+-ATPase in different subfractions of rod outer segments]

Na+, K+-ATPase and Mg++-ATPase are shown to be distributed non-uniformely in different subfractions of the rod outer segments (ROS) of bovine retina. Distribution of the enzymes differs significantly from that of rhodopsin. Predominant portion of Na+, K+-ATPase and Mg++-ATPase is concentrated within the subfractions with the lowest rhodopsin content. The most purified subfractions ROS containing the main amount of rhodopsin lack Na+, K+-ATPase at all, the activity of Mg++-ATPase does not exceed 0,4 plus or minus 0,05 mumoles Pi/mg protein-hour. Distribution of the succinic dehydrogenase is similar to this Na+, K+-ATPase. The data show that Na+, K+-ATPase activity in the ROS fraction is due to the contamination by the inner segment membranes, and that this enzyme is absent in the photoreceptive membranes of ROS.