ON THE MECHANISM OF THE PENETRATION OF THE COLICIN E1 MOLECULE THROUGH THE BACTERIAL ENVELOPE
Abstract
Measurements of the effects of both colicin E1 and a 20Kd proteolytic fragment of the colicin in physiological and artificial systems were used to investigate the penetration of the colicin E1 molecule through the bacterial envelope. Kinetic studies of the inhibition of active transport in E. coli by colicin E1 indicate a transient transenvelope orientation of the colicin. During this period, the colicin molecule is accessible to proteolytic inactivation on the outer surface of the bacteria while inhibiting active transport activity of the inner membrane. Studies of colicin E1 and the 20Kd fragment, in planar and vesicular artificial systems, indicate that the proteins show similar channel-forming, membrane-depolarizing activities. These activies are also similar with respect to requirements for a trans-negative membrane potential, acidic pH, and acidic lipid. The 20Kd fragment is also shown to inhibit active transport in isolated inner membrane vesicles of the E. coli, the target of the colicin E1 molecule. It is concluded that colicin E1 contains a membrane-active domain whose activity in vivo is translocated to the inner membrane, and that an isolated 20Kd C-terminal fragment of the molecule contains this active domain of the intact molecule.
Degree
Ph.D.
Subject Area
Biology
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