Department of Sciences, University of Roma Tre, 00146 Rome, Italy.
National Institute of Nuclear Physics, Roma Tre Section, 00146 Rome, Italy.
Int J Mol Sci. 2023 Feb 15;24(4):3946. doi: 10.3390/ijms24043946.
The Carnitine-Acylcarnitine Carrier is a member of the mitochondrial Solute Carrier Family 25 (SLC25), known as SLC25A20, involved in the electroneutral exchange of acylcarnitine and carnitine across the inner mitochondrial membrane. It acts as a master regulator of fatty acids β-oxidation and is known to be involved in neonatal pathologies and cancer. The transport mechanism, also known as "alternating access", involves a conformational transition in which the binding site is accessible from one side of the membrane or the other. In this study, through a combination of state-of-the-art modelling techniques, molecular dynamics, and molecular docking, the structural dynamics of SLC25A20 and the early substrates recognition step have been analyzed. The results obtained demonstrated a significant asymmetry in the conformational changes leading to the transition from the c- to the m-state, confirming previous observations on other homologous transporters. Moreover, analysis of the MD simulations' trajectories of the apo-protein in the two conformational states allowed for a better understanding of the role of SLC25A20 Asp231His and Ala281Val pathogenic mutations, which are at the basis of Carnitine-Acylcarnitine Translocase Deficiency. Finally, molecular docking coupled to molecular dynamics simulations lend support to the multi-step substrates recognition and translocation mechanism already hypothesized for the ADP/ATP carrier.
肉碱酰基载体蛋白是线粒体溶质载体家族 25（SLC25）的成员，也称为 SLC25A20，参与酰基肉碱和肉碱在内膜之间的电中性交换。它是脂肪酸β-氧化的主要调节因子，已知与新生儿疾病和癌症有关。这种转运机制也称为“交替访问”，涉及构象转变，其中结合位点可从膜的一侧或另一侧进入。在这项研究中，通过结合最先进的建模技术、分子动力学和分子对接，分析了 SLC25A20 的结构动力学和早期底物识别步骤。结果表明，在从 c 态到 m 态的转变过程中，构象变化存在显著的不对称性，这证实了先前对其他同源转运蛋白的观察结果。此外，对apo 蛋白在两种构象状态下的 MD 模拟轨迹进行分析，有助于更好地理解肉碱酰基载体蛋白缺陷的基础——SLC25A20 Asp231His 和 Ala281Val 致病突变的作用。最后，分子对接与分子动力学模拟相结合，支持已假设的 ADP/ATP 载体的多步底物识别和转运机制。
