CLC家族的渠道和運(yùn)輸因子是同型二聚體,，但供在渠道和離子耦合腔（它們在運(yùn)輸因子中協(xié)調(diào)Cl- 和 H+的反向轉(zhuǎn)運(yùn)）中陰離子擴(kuò)散的水孔卻是完全包含在這些同型二聚體的每個(gè)亞單元內(nèi)，說明這些復(fù)合物起“并行通道”的作用,。這種觀點(diǎn)在一項(xiàng)實(shí)驗(yàn)中得到證實(shí)：在該實(shí)驗(yàn)中,，突變被用來使來自大腸桿菌的一個(gè)ClC Cl-/H+“交換器”的二聚體界面失去穩(wěn)定性。這樣得到的渠道是一個(gè)單聚體,，然而它在功能上卻幾乎跟野生型渠道完全相同,。這意味著，跨亞單位的相互作用并不是CLC運(yùn)輸因子中的Cl-/H+交換所必需的,，這便提出一個(gè)問題：野生型運(yùn)輸因子為什么是同型二聚體,？（生物谷Bioon.com）
生物谷推薦原文出處：
Nature doi:10.1038/nature09556
Design, function and structure of a monomeric ClC transporter
Janice L. Robertson,Ludmila Kolmakova-Partensky& Christopher Miller
Channels and transporters of the ClC family cause the transmembrane movement of inorganic anions in service of a variety of biological tasks, from the unusual—the generation of the kilowatt pulses with which electric fish stun their prey—to the quotidian—the acidification of endosomes, vacuoles and lysosomes1. The homodimeric architecture of ClC proteins, initially inferred from single-molecule studies of an elasmobranch Cl? channel2 and later confirmed by crystal structures of bacterial Cl?/H+ antiporters3, 4, is apparently universal. Moreover, the basic machinery that enables ion movement through these proteins—the aqueous pores for anion diffusion in the channels and the ion-coupling chambers that coordinate Cl? and H+ antiport in the transporters—are contained wholly within each subunit of the homodimer. The near-normal function of a bacterial ClC transporter straitjacketed by covalent crosslinks across the dimer interface and the behaviour of a concatemeric human homologue argue that the transport cycle resides within each subunit and does not require rigid-body rearrangements between subunits5, 6. However, this evidence is only inferential, and because examples are known in which quaternary rearrangements of extramembrane ClC domains that contribute to dimerization modulate transport activity7, we cannot declare as definitive a ‘parallel-pathways’ picture in which the homodimer consists of two single-subunit transporters operating independently. A strong prediction of such a view is that it should in principle be possible to obtain a monomeric ClC. Here we exploit the known structure of a ClC Cl?/H+ exchanger, ClC-ec1 from Escherichia coli, to design mutants that destabilize the dimer interface while preserving both the structure and the transport function of individual subunits. The results demonstrate that the ClC subunit alone is the basic functional unit for transport and that cross-subunit interaction is not required for Cl?/H+ exchange in ClC transporters.
