Component of the MICOS complex, a large protein complex of the mitochondrial inner membrane that plays crucial roles in the maintenance of crista junctions, inner membrane architecture, and formation of contact sites to the outer membrane. Has also been shown to function as a transcription factor which binds to the BAG1 promoter and represses BAG1 transcription. Plays an important role in the maintenance of the MICOS complex stability and the mitochondrial cristae morphology. Component of the mitochondrial contact site and cristae organizing system (MICOS) complex, composed of at least MICOS10/MIC10, CHCHD3/MIC19, CHCHD6/MIC25, APOOL/MIC27, IMMT/MIC60, APOO/MIC23/MIC26 and MICOS13/MIC13. This complex was also known under the names MINOS or MitOS complex. The MICOS complex associates with mitochondrial outer membrane proteins SAMM50, MTX1 and MTX2 (together described as components of the mitochondrial outer membrane sorting assembly machinery (SAM) complex) and DNAJC11, mitochondrial inner membrane protein TMEM11 and with HSPA9. The MICOS and SAM complexes together with DNAJC11 are part of a large protein complex spanning both membranes termed the mitochondrial intermembrane space bridging (MIB) complex (By similarity). Interacts with HSPA1A/HSPA1B and OPA1, preferentially with the soluble OPA1 form. Belongs to the MICOS complex subunit Mic19 family. Metazoan Mic19 subfamily.