Energy-coupling factor (ECF)-type ATP-binding cassette (ABC) transporters catalyze membrane transport of micronutrients in prokaryotes. Crystal structures and biochemical characterization have revealed that ECF transporters are mechanistically distinct from other ABC transport systems. Notably, ECF transporters make use of small integral membrane subunits (S-components) that are predicted to topple over in the membrane when carrying the bound substrate from the extracellular side of the bilayer to the cytosol. Here, we review the phylogenetic diversity of ECF transporters as well as recent structural and biochemical advancements that have led to the postulation of conceptually different mechanistic models. These models can be described as power stroke and thermal ratchet. Structural data indicate that the lipid composition and bilayer structure are likely to have great impact on the transport function. We argue that study of ECF transporters could lead to generic insight into membrane protein structure, dynamics, and interaction.

中文翻译：

---

ECF型ATP结合盒式转运蛋白。

能量耦合因子（ECF）型ATP结合盒（ABC）转运蛋白催化原核生物中微量营养元素的膜转运。晶体结构和生化特征表明，ECF转运蛋白在机理上不同于其他ABC转运系统。值得注意的是，ECF转运蛋白利用小的整体膜亚基（S成分），当将结合的底物从双层的细胞外侧运送到细胞质时，预计会在膜中翻倒。在这里，我们回顾了ECF转运蛋白的系统发育多样性，以及最近在结构和生化方面的进展，这些进展已导致提出了概念上不同的机械模型。这些模型可以描述为动力冲程和热棘轮。结构数据表明脂质组成和双层结构可能对转运功能有很大影响。我们认为对ECF转运蛋白的研究可能会导致对膜蛋白结构，动力学和相互作用的普遍了解。