BINDING PROTEINS AND MEMBRANE TRANSPORT*

Bacterial cells have developed two basic types of active transport systems. One of these transport systems is a membrane-bound system and can be ob-served in membrane vesicle preparations prepared by the methods described in the previous presentation by Kaback. ' Dr. Kaback described the transport properties of membrane vesicles from gram-negative bacteria that retain the membrane-bound transport system. He has shown that these membranes retain all components of the transport system except an energy source, which is necessary for the system to produce active transport. The membrane-bound systems derive their energy from an "energy-rich membrane state, " which can be formed in a variety of ways such as respiration, ATP hydrolysis, or proton gradient-forming conditions. " ' A second type of active transport system that I would like to describe is a system that requires a shockable binding protein to produce active trans-port."'-' ' It appears that the binding protein transport systems obtain their cellular energy more directly from phosphate bound energy derived fro