Institut für Pharmazie und Biochemie, Johannes-Gutenberg-Universität Mainz, 55128 Mainz, Germany.
Laboratoire de bioelectrochimie et spectroscopie, UMR 7140, CNRS Université de Strasbourg, 1 rue Blaise Pascal, 67000 Strasbourg, Germany.
J Biol Chem. 2018 May 25;293(21):8230-8241. doi: 10.1074/jbc.RA117.000991. Epub 2018 Apr 4.
The "inner membrane-associated protein of 30 kDa" (IM30), also known as "vesicle-inducing protein in plastids 1" (Vipp1), is found in the majority of photosynthetic organisms that use oxygen as an energy source, and its occurrence appears to be coupled to the existence of thylakoid membranes in cyanobacteria and chloroplasts. IM30 is most likely involved in thylakoid membrane biogenesis and/or maintenance, and has recently been shown to function as a membrane fusion protein in presence of Mg However, the precise role of Mg in this process and its impact on the structure and function of IM30 remains unknown. Here, we show that Mg binds directly to IM30 with a binding affinity of ∼1 mm Mg binding compacts the IM30 structure coupled with an increase in the thermodynamic stability of the proteins' secondary, tertiary, and quaternary structures. Furthermore, the structural alterations trigger IM30 double ring formation because of increased exposure of hydrophobic surface regions. However, Mg-triggered exposure of hydrophobic surface regions most likely modulates membrane binding and induces membrane fusion.
“30kDa 内膜相关蛋白”（IM30），也称为“质体囊泡诱导蛋白 1”（Vipp1），存在于大多数利用氧气作为能源的光合生物中，其存在似乎与蓝细菌和叶绿体中类囊体膜的存在有关。IM30 很可能参与类囊体膜的生物发生和/或维持，并且最近已被证明在存在 Mg 的情况下作为膜融合蛋白发挥作用。然而，Mg 在这个过程中的精确作用及其对 IM30 结构和功能的影响仍然未知。在这里，我们表明 Mg 与 IM30 直接结合，结合亲和力约为 1mM。Mg 结合使 IM30 结构紧凑，同时增加蛋白质二级、三级和四级结构的热力学稳定性。此外，结构的改变引发了 IM30 双环的形成，因为疏水面区域的暴露增加。然而，Mg 引发的疏水面区域的暴露很可能调节膜结合并诱导膜融合。
