ABC transporters facilitate the movement of diverse molecules across cellular membranes, but how their activity is regulated post-translationally is not well understood. Here we report the crystal structure of MlaFB from E. coli, the cytoplasmic portion of the larger MlaFEDB ABC transporter complex, which drives phospholipid trafficking across the bacterial envelope to maintain outer membrane integrity. MlaB, a STAS domain protein, binds the ABC nucleotide binding domain, MlaF, and is required for its stability. Our structure also implicates a unique C-terminal tail of MlaF in self-dimerization. Both the C-terminal tail of MlaF and the interaction with MlaB are required for the proper assembly of the MlaFEDB complex and its function in cells. This work leads to a new model for how an important bacterial lipid transporter may be regulated by small proteins, and raises the possibility that similar regulatory mechanisms may exist more broadly across the ABC transporter family.

中文翻译：

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MlaFB 的结构揭示了 ABC 转运蛋白调节的新机制


ABC 转运蛋白促进不同分子跨细胞膜的移动，但它们的活性如何在翻译后调节尚不清楚。在这里，我们报告了来自大肠杆菌的 MlaFB 的晶体结构，它是较大的 MlaFEDB ABC 转运蛋白复合物的细胞质部分，该复合物驱动磷脂穿过细菌包膜运输以维持外膜完整性。 MlaB 是一种 STAS 结构域蛋白，可结合 ABC 核苷酸结合结构域 MlaF，并且是其稳定性所必需的。我们的结构还暗示了 MlaF 在自二聚化中独特的 C 末端尾部。 MlaF C 末端尾部以及与 MlaB 的相互作用都是 MlaFEDB 复合物的正确组装及其在细胞中的功能所必需的。这项工作为小蛋白如何调节重要的细菌脂质转运蛋白提供了一个新模型，并提出了类似的调节机制可能更广泛地存在于 ABC 转运蛋白家族中的可能性。