Two-State Exchange Dynamics in Membrane-Embedded Oligosaccharyltransferase Observed in Real-Time by High-Speed AFM

Immobilization of lipid nanorods onto two-dimensional crystals of protein tamavidin 2 for high-speed atomic force microscopy

High-speed atomic force microscopy is a technique that allows real-time observation of biomolecules and biological phenomena reconstituted on a substrate. Here, we present a protocol for immobilizing lipid nanorods onto two-dimensional crystals of biotin-binding protein tamavidin 2. We describe steps for the preparation of tamavidin 2 protein, lipid nanorods, and two-dimensional crystals of tamavidin 2 formed on mica. Immobilized lipid nanorods are one of the useful tools for observation of specific proteins in action. For complete details on the use and execution of this protocol, please refer to Fukuda et al. (2023).1.

The mitochondrial intermembrane space protein mitofissin drives mitochondrial fission required for mitophagy

Mitophagy plays an important role in mitochondrial homeostasis by selective degradation of mitochondria. During mitophagy, mitochondria should be fragmented to allow engulfment within autophagosomes, whose capacity is exceeded by the typical mitochondria mass. However, the known mitochondrial fission factors, dynamin-related proteins Dnm1 in yeasts and DNM1L/Drp1 in mammals, are dispensable for mitophagy. Here, we identify Atg44 as a mitochondrial fission factor that is essential for mitophagy in yeasts, and we therefore term Atg44 and its orthologous proteins mitofissin. In mitofissin-deficient cells, a part of the mitochondria is recognized by the mitophagy machinery as cargo but cannot be enwrapped by the autophagosome precursor, the phagophore, due to a lack of mitochondrial fission. Furthermore, we show that mitofissin directly binds to lipid membranes and brings about lipid membrane fragility to facilitate membrane fission. Taken together, we propose that mitofissin acts directly on lipid membranes to drive mitochondrial fission required for mitophagy.