Stettler Philip, Schimanski Bernd, Aeschlimann Salome, Schneider André
Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland.
Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.
PLoS Pathog. 2024 Dec 2;20(12):e1012635. doi: 10.1371/journal.ppat.1012635. eCollection 2024 Dec.
The parasitic protozoan Trypanosoma brucei has a single unit mitochondrial genome linked to the basal body of the flagellum via the tripartite attachment complex (TAC). The TAC is crucial for mitochondrial genome segregation during cytokinesis. At the core of the TAC, the outer membrane protein TAC60 binds to the inner membrane protein p166, forming a permanent contact site between the two membranes. Although contact sites between mitochondrial membranes are common and serve various functions, their molecular architecture remains largely unknown. This study elucidates the interaction interface of the TAC60-p166 contact site. Using in silico, in vitro, and mutational in vivo analyses, we identified minimal binding segments between TAC60 and p166. The p166 binding site in TAC60 consists of a short kinked α-helix that interacts with the C-terminal α-helix of p166. Despite the presence of conserved charged residues in either protein, electrostatic interactions are not necessary for contact site formation. Instead, the TAC60-p166 interaction is driven by the hydrophobic effect, as converting conserved hydrophobic residues in either protein to hydrophilic amino acids disrupts the contact site.
寄生原生动物布氏锥虫具有单个线粒体基因组，该基因组通过三联体附着复合体（TAC）与鞭毛的基体相连。TAC对于胞质分裂期间线粒体基因组的分离至关重要。在TAC的核心，外膜蛋白TAC60与内膜蛋白p166结合，在两个膜之间形成一个永久的接触位点。尽管线粒体膜之间的接触位点很常见且具有多种功能，但其分子结构在很大程度上仍不清楚。本研究阐明了TAC60-p166接触位点的相互作用界面。通过计算机模拟、体外实验和体内突变分析，我们确定了TAC60和p166之间的最小结合片段。TAC60中的p166结合位点由一个短的扭结α螺旋组成，该螺旋与p166的C端α螺旋相互作用。尽管两种蛋白质中都存在保守的带电荷残基，但静电相互作用对于接触位点的形成并非必需。相反，TAC60-p166相互作用是由疏水作用驱动的，因为将两种蛋白质中保守的疏水残基转化为亲水氨基酸会破坏接触位点。
