Liganded and unliganded receptors interact with equal affinity with the membrane complex of periplasmic permeases, a subfamily of traffic ATPases
Liganded and unliganded receptors interact with equal affinity with the membrane complex of periplasmic permeases, a subfamily of traffic ATPases
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DOI：
10.1074/jbc.271.24.14264
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发表时间：
1996-06-14
影响因子：
4.8
通讯作者：
Nikaido, K
中科院分区：
文献类型：
--
作者：
Ames, GFL;Liu, CE;Nikaido, K
组氨酸结合蛋白HisJ是鼠伤寒沙门氏菌周质内组氨酸渗透酶的可溶性受体，该受体与周质中的底物结合，与膜结合的复合体相互作用，传递跨膜信号以水解三磷酸腺苷，并释放配体进行转位。与其他周质受体一样，HisJ有两个叶，它们在未连接的结构(开放构象)中分开，在配基结构(闭合构象)中紧密连接，深埋配体，这种受体可能与膜结合的复合体以高亲和力的配基构象相互作用，在底物转位时亲和力降低，从而释放。在这里，我们证明了与目前的假设相反，连接和未连接的受体对膜结合复合体具有相同的亲和力，亲和力是通过化学交联和共沉淀过程来测量的，ATPase活性测定也被用来证明非连接受体与膜结合复合体的相互作用，这些发现支持一个新的转运机制模型，在该模型中，可溶性受体独立于普遍接受的高-低亲和力开关发挥作用。
The histidine-binding protein, HisJ, is the soluble receptor for the periplasmic histidine permease of Salmonella typhimurium, The receptor binds the substrate in the periplasm, interacts with the membrane-bound complex, transmits a transmembrane signal to hydrolyze ATP, and releases the ligand for translocation, HisJ, like other periplasmic receptors, has two lobes that are apart in the unliganded structure (open conformation) and drawn close together in the liganded structure (closed conformation), burying deeply the ligand, Such receptors are postulated to interact with the membrane bound complex with high affinity in their liganded con formation, and, upon substrate translocation, to undergo a reduction in affinity and therefore be released, Here we show that in contrast to the current postulate, liganded and unliganded receptors have equal affinity for the membrane-bound complex, The affinity is measured both by chemical cross-linking and co-sedimentation procedures, An ATPase activity assay is also used to demonstrate the interaction of unliganded receptor with the membrane-bound complex, These findings support a new model for the transport mechanism, in which the soluble receptor functions independently of the commonly accepted high-low affinity switch.