EVOLUTIONARY RELATIONSHIP OF UPTAKE SYSTEMS FOR BIOPOLYMERS IN ESCHERICHIA-COLI - CROSS-COMPLEMENTATION BETWEEN THE TONB EXBB EXBD AND THE TOLA TOLQ TOLR PROTEINS
EVOLUTIONARY RELATIONSHIP OF UPTAKE SYSTEMS FOR BIOPOLYMERS IN ESCHERICHIA-COLI - CROSS-COMPLEMENTATION BETWEEN THE TONB EXBB EXBD AND THE TOLA TOLQ TOLR PROTEINS
复制标题
DOI：
10.1111/j.1365-2958.1993.tb01570.x
复制
发表时间：
1993-04-01
影响因子：
3.6
通讯作者：
HERRMANN, C
中科院分区：
文献类型：
--
作者：
BRAUN, V;HERRMANN, C
大肠杆菌有两个能量耦合的输入系统，通过这两个系统，低浓度和太大而不允许通过孔蛋白扩散的物质被转移到外膜上。B组粘菌素、铁铁载体和维生素B-12通过TonB-ExbB-ExbD摄取，A组粘菌素通过TOLA-TolQ-TolR系统摄取。两个系统之间的交叉互补表现为：携带exbB exbD基因的tolQ-tolR突变株对A组粘连素敏感，而携带质粒编码的tolQ-tolR的exbB-exbD突变株对B组粘连素敏感。TolQ-TolR通过TonB相互作用，ExbB-ExbD通过Tola与外膜受体和粘连素相互作用。在缺乏TonB的细胞中，通过TonB的ExbB ExbD活性较高，当Tola缺失时，通过TonB的TolQ TolR的活性增加。非常独特的Tola和TonB蛋白分别介导与A组和B组受体的排他性相互作用。ExbB-TolR和ExbD-TolQ混合物显示exbB、exbD和tolQ突变体几乎没有互补，表明ExbB与ExbD、TolQ与TolR共同进化。ExbB-ExbD和TolQ-TolR的序列同源性和相互功能替换表明两个输入系统由一个输入系统进化而来。
Escherichia coli possesses two energy-coupled import systems through which substances of low concentration and of a size too large to permit diffusion through the porins are translocated across the outer membrane. Group B colicins, ferric siderophores and vitamin B-12 are taken up via the TonB-ExbB-ExbD, group A colicins via the TolA-TolQ-TolR system. Cross-complementation between the two systems was demonstrated in that tolQ tolR mutants transformed with plasmids carrying exbB exbD became sensitive to group A colicins, and exbB exbD mutants transformed with plasmid-encoded tolQ tolR became sensitive to group B colicins. TolQ-TolR interacted through TonB, and ExbB-ExbD interacted through TolA with the outer membrane receptors and colicins. Activity of ExbB ExbD via TolA was higher in cells lacking TonB, and activity of TolQ TolR via TonB was increased when TolA was missing. The very distinct TolA and TonB proteins mediate exclusive interaction with group A and group B receptors, respectively. ExbB-TolR and ExbD-TolQ mixtures showed little if any complementation of exbB exbD and tolQ tolR mutants indicating co-evolution of ExbB with ExbD and TolQ with TolR. Sequence homology and mutual functional substitution of ExbB-ExbD and TolQ-TolR suggest the evolution of the two import systems from a single import system.