Porin Associates with Tom22 to Regulate the Mitochondrial Protein Gate Assembly

• DOI: 10.1016/j.molcel.2019.01.003
• Publication Date: 2019-02-10T12:38:44Z
• Authors: Haruka Sakaue; Takuya Shiota; Naoya Ishizaka; Shin Kawano; Yasushi Tamura; Kher Shing Tan; Kenichiro Imai; Chie Motono; Takatsugu Hirokawa; Kentaro Taki; Non Miyata; Osamu Kuge; Trevor Lithgow; Toshiya Endo
• Keywords: 0303 health sciences; Saccharomyces cerevisiae Proteins; Cell Cycle; Porins; Biological Transport; Saccharomyces cerevisiae; Mitochondrial Membrane Transport Proteins; Mitochondria; 03 medical and health sciences; Mitochondrial Membranes; Mitochondrial Precursor Protein Import Complex Proteins; HSP70 Heat-Shock Proteins; Phosphorylation; Carrier Proteins; Protein Binding

Mitochondria import nearly all of their resident proteins from the cytosol, and the TOM complex functions as their entry gate. The TOM complex undergoes a dynamic conversion between the majority population of a three-channel gateway ("trimer") and the minor population that lacks Tom22 and has only two Tom40 channels ("dimer"). Here, we found that the porin Por1 acts as a sink to bind newly imported Tom22. This Por1 association thereby modulates Tom22 integration into the TOM complex, guaranteeing formation of the functional trimeric TOM complex. Por1 sequestration of Tom22 dissociated from the trimeric TOM complex also enhances the dimeric TOM complex, which is preferable for the import of TIM40/MIA-dependent proteins into mitochondria. Furthermore, Por1 appears to contribute to cell-cycle-dependent variation of the functional trimeric TOM complex by chaperoning monomeric Tom22, which arises from the cell-cycle-controlled variation of phosphorylated Tom6.