30kDa的内膜相关蛋白(IM30)对于叶绿体和蓝细菌中类囊体膜系统的发育和维持至关重要。虽然它的确切生理功能仍在争论中,最近有人建议IM30(至少)具有双重功能,并且该蛋白质参与类囊体膜的稳定以及Mg2依赖性膜融合。IM30与带负电荷的膜脂结合,优先在应力膜区域,其中质子可能从类囊体管腔泄漏到叶绿体基质或蓝细菌细胞质中,分别。这里我们在体外显示IM30膜结合,以及膜融合,在酸性环境中强烈增加。这种增强的活性涉及蛋白质结构的重排。我们建议这种酸诱导的转变是一种机制的一部分,该机制允许IM30(i)感觉类囊体膜上的质子泄漏位点,(ii)优先绑定在那里,和(iii)通过膜融合过程密封渗漏膜区域。
The inner membrane-associated protein of 30 kDa (
IM30) is crucial for the development and maintenance of the thylakoid membrane system in chloroplasts and cyanobacteria. While its exact physiological function still is under debate, it has recently been suggested that
IM30 has (at least) a dual function, and the protein is involved in stabilization of the thylakoid membrane as well as in Mg2+-dependent membrane fusion.
IM30 binds to negatively charged membrane lipids, preferentially at stressed membrane regions where protons potentially leak out from the thylakoid lumen into the chloroplast stroma or the cyanobacterial cytoplasm, respectively. Here we show in vitro that
IM30 membrane binding, as well as membrane fusion, is strongly increased in acidic environments. This enhanced activity involves a rearrangement of the protein structure. We suggest that this acid-induced transition is part of a mechanism that allows
IM30 to (i) sense sites of proton leakage at the thylakoid membrane, to (ii) preferentially bind there, and to (iii) seal leaky membrane regions via membrane fusion processes.