Bao Huan, Dalal Kush, Wang Victor, Rouiller Isabelle, Duong Franck
Department of Biochemistry & Molecular Biology, University of British Columbia, Vancouver, Canada.
Biochim Biophys Acta. 2013 Aug;1828(8):1723-30. doi: 10.1016/j.bbamem.2013.03.024. Epub 2013 Apr 2.
The coupling between ATP hydrolysis and substrate transport remains a key question in the understanding of ABC-mediated transport. We show using the MalFGK2 complex reconstituted into nanodiscs, that membrane lipids participate directly to the coupling reaction by stabilizing the transporter in a low energy conformation. When surrounded by short acyl chain phospholipids, the transporter is unstable and hydrolyzes large amounts of ATP without inducing maltose. The presence of long acyl chain phospholipids stabilizes the conformational dynamics of the transporter, reduces its ATPase activity and restores dependence on maltose. Membrane lipids therefore play an essential allosteric function, they restrict the transporter ATPase activity to increase coupling to the substrate. In support to the notion, we show that increasing the conformational dynamics of MalFGK2 with mutations in MalF increases the transporter ATPase activity but decreases the maltose transport efficiency.
ATP水解与底物转运之间的偶联仍是理解ABC介导转运的关键问题。我们利用重构到纳米盘里的MalFGK2复合物表明，膜脂通过将转运蛋白稳定在低能构象而直接参与偶联反应。当被短酰基链磷脂包围时，转运蛋白不稳定，会水解大量ATP而不诱导麦芽糖转运。长酰基链磷脂的存在稳定了转运蛋白的构象动力学，降低其ATP酶活性并恢复对麦芽糖的依赖性。因此，膜脂发挥着至关重要的变构功能，它们限制转运蛋白的ATP酶活性以增强与底物的偶联。为支持这一观点，我们表明通过MalF中的突变增加MalFGK2的构象动力学可提高转运蛋白的ATP酶活性，但会降低麦芽糖转运效率。
