Volume 33 Issue 6
Dec.  2020
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Yun Huang, Hao-chen Xu, Jie-lou Liao. Coarse-Grained Free-Energy Simulations of Conformational State Transitions in an Adenosine 5′-Triphosphate-binding Cassette Exporter[J]. Chinese Journal of Chemical Physics , 2020, 33(6): 712-716. doi: 10.1063/1674-0068/cjcp1908149
 Citation: Yun Huang, Hao-chen Xu, Jie-lou Liao. Coarse-Grained Free-Energy Simulations of Conformational State Transitions in an Adenosine 5′-Triphosphate-binding Cassette Exporter[J]. Chinese Journal of Chemical Physics , 2020, 33(6): 712-716.

# Coarse-Grained Free-Energy Simulations of Conformational State Transitions in an Adenosine 5′-Triphosphate-binding Cassette Exporter

##### doi: 10.1063/1674-0068/cjcp1908149
• Corresponding author: Jie-lou Liao, E-mail: liaojl@ustc.edu.cn
• Accepted Date: 2019-08-30
• Publish Date: 2020-12-27
• ATP-binding cassette exporters transport many substrates out of cellular membranes via alternating between inward-facing and outward-facing conformations. Despite extensive research efforts over the past decades, understanding of the molecular mechanism remains elusive. As these large-scale conformational movements are global and collective, we have previously performed extensive coarse-grained molecular dynamics simulations of the potential of mean force along the conformational transition pathway [J. Phys. Chem. B 119 , 1295 (2015)]. However, the occluded conformational state, in which both the internal and external gate are closed, was not determined in the calculated free energy profile. In this work, we extend the above methods to the calculation of the free energy profile along the reaction coordinate, $d_1$$-$$d_2$, which are the COM distances between the two sides of the internal ($d_1$) and the external gate ($d_2$). The potential of mean force is thus obtained to identify the transition pathway, along which several outward-facing, inward-facing, and occluded state structures are predicted in good agreement with structural experiments. Our coarse-grained molecular dynamics free-energy simulations demonstrate that the internal gate is closed before the external gate is open during the inward-facing to outward-facing transition and vice versa during the inward-facing to outward-facing transition. Our results capture the unidirectional feature of substrate translocation via the exporter, which is functionally important in biology. This finding is different from the previous result, in which both the internal and external gates are open reported in an X-ray experiment [Proc. Natl. Acad. Sci. USA 104 , 19005 (2007)]. Our study sheds light on the molecular mechanism of the state transitions in an ATP-binding cassette exporter.
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###### 通讯作者: 陈斌, bchen63@163.com
• 1.

沈阳化工大学材料科学与工程学院 沈阳 110142

Figures(5)

## Coarse-Grained Free-Energy Simulations of Conformational State Transitions in an Adenosine 5′-Triphosphate-binding Cassette Exporter

##### doi: 10.1063/1674-0068/cjcp1908149
###### Corresponding author:Jie-lou Liao, E-mail: liaojl@ustc.edu.cn

Abstract: ATP-binding cassette exporters transport many substrates out of cellular membranes via alternating between inward-facing and outward-facing conformations. Despite extensive research efforts over the past decades, understanding of the molecular mechanism remains elusive. As these large-scale conformational movements are global and collective, we have previously performed extensive coarse-grained molecular dynamics simulations of the potential of mean force along the conformational transition pathway [J. Phys. Chem. B 119 , 1295 (2015)]. However, the occluded conformational state, in which both the internal and external gate are closed, was not determined in the calculated free energy profile. In this work, we extend the above methods to the calculation of the free energy profile along the reaction coordinate, $d_1$$-$$d_2$, which are the COM distances between the two sides of the internal ($d_1$) and the external gate ($d_2$). The potential of mean force is thus obtained to identify the transition pathway, along which several outward-facing, inward-facing, and occluded state structures are predicted in good agreement with structural experiments. Our coarse-grained molecular dynamics free-energy simulations demonstrate that the internal gate is closed before the external gate is open during the inward-facing to outward-facing transition and vice versa during the inward-facing to outward-facing transition. Our results capture the unidirectional feature of substrate translocation via the exporter, which is functionally important in biology. This finding is different from the previous result, in which both the internal and external gates are open reported in an X-ray experiment [Proc. Natl. Acad. Sci. USA 104 , 19005 (2007)]. Our study sheds light on the molecular mechanism of the state transitions in an ATP-binding cassette exporter.

Yun Huang, Hao-chen Xu, Jie-lou Liao. Coarse-Grained Free-Energy Simulations of Conformational State Transitions in an Adenosine 5′-Triphosphate-binding Cassette Exporter[J]. Chinese Journal of Chemical Physics , 2020, 33(6): 712-716. doi: 10.1063/1674-0068/cjcp1908149
 Citation: Yun Huang, Hao-chen Xu, Jie-lou Liao. Coarse-Grained Free-Energy Simulations of Conformational State Transitions in an Adenosine 5′-Triphosphate-binding Cassette Exporter[J]. Chinese Journal of Chemical Physics , 2020, 33(6): 712-716.
Reference (36)

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