Order–disorder skewness in alpha-synuclein: a key mechanism to recognize membrane curvature

2022

Chem. Sci.

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Section: Methodsmentioning

confidence: 99%

Synaptotagmin-1 C2B domains cooperatively stabilize the fusion stalk via a master-servant mechanism

Bartolo

2022

Chem. Sci.

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“…Molecular dynamics simulations used the semiisotropic NPT ensemble and a time step of 20fs in all cases. The temperature was set to T=303.15K 6,[45][46][47][48] and was controlled by a V-rescale thermostat 49 with a coupling constant of 1ps. The pressure was set at 1.0bar with the compressibility equal to 3x10 −4 bar −1 , using the Parrinello-Rahman barostat 50 with a 12ps time constant.…”

Section: Methodsmentioning

confidence: 99%

Synaptotagmin-1 C2B domains cooperatively stabilize the fusion stalk via a master-servant mechanism

Bartolo

2021

Preprint

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Synaptotagmin-1 is a low-affinity Ca2+ sensor that triggers synchronous vesicle fusion. It contains two similar C2 domains (C2A and C2B) that cooperate in membrane binding, being the C2B domain the main responsible for the membrane fusion process due to its polybasic patch KRLKKKKTTIKK (321-332). In this work, a master-servant mechanism between two identical C2B domains is shown to control the formation of the fusion stalk. Two regions in C2B are essential for the process, the well-known polybasic patch and a recently described pair of arginines (398,399). The master domain shows strong PIP2 interactions with its polybasic patch and its pair of arginines. At the same time, the servant analogously cooperates with the master to reduce the total work to form the fusion stalk. The strategic mutation (T328E,T329E) in both master and servant domains disrupts the cooperative mechanism, drastically increasing the free energy needed to induce the fusion stalk, however with negligible effects on the master domain interactions with PIP2. These data point to a difference in the behavior of the servant domain, which is unable to sustain its PIP2 interactions neither through its polybasic patch nor through its pair of arginines, in the end losing its ability to assist the master in the formation of the fusion stalk.

“…Molecular dynamics simulations were performed with GROMACS-2020.2 [43][44][45] with the semi-isotropic NPT ensemble and a time step of 20fs in all cases, with the exception of the simulation of a single SMAC solvated in water (no bilayers) where the isotropic ensemble was used instead. The temperature, T=303.15K [46][47][48][49][50] , was controlled by a V-rescale thermostat 51 using a coupling constant of 1ps. The pressure was maintained at 1.0bar and compressibility was set to 3x10 −4 bar −1 .…”

Section: Methodsmentioning

confidence: 99%

Artificial stabilization of the fusion pore by intra-organelle styrene-maleic acid copolymers

Caparotta

Puiatti

2021

Preprint

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Styrene-maleic acid copolymers have become an advantageous detergent-free alternative for membrane protein isolation. Since their discovery, experimental membrane protein extraction and purification by keeping intact their lipid environment has become significantly easier. With the aim of identifying new applications of these interesting copolymers, their molecular binding and functioning mechanisms have recently been intense objects of study. In this work, we describe the use of styrene-maleic acid copolymers as an artificial tool to stabilize the fusion pore. We show that when these copolymers circumscribe the water channel that defines the fusion pore, they keep it from shrinking and closing. We describe how only intra-organelle copolymers have stabilizing capabilities while extra-organelle ones have negligible or even contrary effects on the fusion pore life-time.