Membrane Biophysical Studies of the Colicin E1 Channel

Colicins是由某些菌株在细菌细胞生长过程中产生的有毒蛋白质，它们通常是在应对一系列代谢挑战时产生的，包括DNA损伤、厌氧、分解代谢抑制和营养耗竭。Colicin E1(Cole1)是形成通道的Colicins的一员，它还包括Colicins A、B、Ia、Ib、N和K。Colicin的三维结构揭示了Colicin的三个结构域：受体结合、易位和通道结构域。受体结合区通过与细菌外膜上的维生素B12受体结合，启动毒素进入靶细胞。接下来，易位结构域与三聚体β桶TolC外膜受体结合，通过该受体将结肠素运输到目标细菌的周质中。在一系列步骤中，cole1依次展开、结合并自发插入膜中，形成关闭的通道状态。该通道在膜电位为负的情况下开放，并通过逃逸细胞内的Na+、K+和H+等离子引起宿主细胞胞质膜的去极化。

Colicins are toxic proteins produced by certain strains of E. coli during bacterial cell growth and they are often produced in response to a host of metabolic challenges, including DNA damage, anaerobiosis, catabolite repression and nutrient depletion. Colicin E1 (colE1) is a member of the channel-forming colicins, which also includes colicins A, B, Ia, Ib, N and K. The three-dimensional structures of colicins reveal the presence of three domains: receptor binding, translocation, and channel domains. The receptor-binding domain initiates toxin entry into target cells by binding with the vitamin B12 receptor on the bacterial outer membrane. Next, the translocation domain associates with the trimeric beta-barrel TolC outer membrane receptor, through which the colicin is transported into the periplasm of the target bacterium. In a series of steps, colE1 sequentially unfolds, binds and spontaneously inserts into the membrane to form a closed channel state. The channel opens in the presence of a trans-negative membrane potential and causes depolarization of the host cell cytoplasmic membrane through the escape of cellular ions such as Na+, K+, and H+.