In Nature structural & molecular biology ; h5-index 83.0
Mitochondrial β-barrel proteins are essential for the transport of metabolites, ions and proteins. The sorting and assembly machinery (SAM) mediates their folding and membrane insertion. We report the cryo-electron microscopy structure of the yeast SAM complex carrying an early eukaryotic β-barrel folding intermediate. The lateral gate of Sam50 is wide open and pairs with the last β-strand (β-signal) of the substrate-the 19-β-stranded Tom40 precursor-to form a hybrid barrel in the membrane plane. The Tom40 barrel grows and curves, guided by an extended bridge with Sam50. Tom40's first β-segment (β1) penetrates into the nascent barrel, interacting with its inner wall. The Tom40 amino-terminal segment then displaces β1 to promote its pairing with Tom40's last β-strand to complete barrel formation with the assistance of Sam37's dynamic α-protrusion. Our study thus reveals a multipoint guidance mechanism for mitochondrial β-barrel folding.
Takeda Hironori, Busto Jon V, Lindau Caroline, Tsutsumi Akihisa, Tomii Kentaro, Imai Kenichiro, Yamamori Yu, Hirokawa Takatsugu, Motono Chie, Ganesan Iniyan, Wenz Lena-Sophie, Becker Thomas, Kikkawa Masahide, Pfanner Nikolaus, Wiedemann Nils, Endo Toshiya
2023-Jan-05
