The mitochondrial inner membrane consists of two domains, inner boundary 
membrane and cristae membrane that are connected by crista junctions. 
Mitofilin/Fcj1 was reported to be involved in formation of crista junctions, 
however, different views exist on its function and possible partner proteins. We 
report that mitofilin plays a dual role. Mitofilin is part of a large inner 
membrane complex, and we identify five partner proteins as constituents of the 
mitochondrial inner membrane organizing system (MINOS) that is required for 
keeping cristae membranes connected to the inner boundary membrane. 
Additionally, mitofilin is coupled to the outer membrane and promotes protein 
import via the mitochondrial intermembrane space assembly pathway. Our findings 
indicate that mitofilin is a central component of MINOS and functions as a 
multifunctional regulator of mitochondrial architecture and protein biogenesis.