Structure and function of mitochondria are intimately linked. In a search for 
components that participate in building the elaborate architecture of this 
complex organelle we have identified Aim24, an inner membrane protein. Aim24 
interacts with the MICOS complex that is required for the formation of crista 
junctions and contact sites between inner and outer membranes. Aim24 is 
necessary for the integrity of the MICOS complex, for normal respiratory growth 
and mitochondrial ultrastructure. Modification of MICOS subunits Mic12 or Mic26 
by His-tags in the absence of Aim24 leads to complete loss of cristae and 
respiratory complexes. In addition, the level of tafazzin, a cardiolipin 
transacylase, is drastically reduced and the composition of cardiolipin is 
modified like in mutants lacking tafazzin. In conclusion, Aim24 by interacting 
with the MICOS complex plays a key role in mitochondrial architecture, 
composition and function. DOI: http://dx.doi.org/10.7554/eLife.01684.001.