Integrative structure determination of a human mitochondrial contact site and cristae organizing system (MICOS) sub-assembly

Abstract

The Mitochondrial contact site and Cristae Organizing System (MICOS) complex is an inner mitochondrial membrane (IMM) assembly present at the cristae junction. It is responsible for regulating cristae formation and remodeling. However, its structure is not known. We applied Bayesian integrative structure determination to characterize the structure of the Mic60, Mic19, Mic10, and Mic13-containing MICOS sub-assembly combining AlphaFold predictions with data from crosslinking mass spectrometry, biochemical assays, electron tomography, homology modeling, and sequence alignments. The integrative structure revealed novel mutual interfaces among Mic10N,C, Mic60LBS1,LBS2,mitofilin, and Mic13central,C. Several likely-pathogenic missense mutations also localize to these novel interfaces, highlighting their importance. Further, we investigated some of these interactions using binding assays on purified proteins and demonstrated direct interactions among Mic10-Mic13-Mic60. Our results support a bridging role for Mic13 in the MICOS assembly, by binding Mic10 in the IMM-proximal region and Mic60 in the intermembrane space. Taken together, our integrative approach sheds light on the structure and assembly of the MICOS complex.