Involved in mitochondrial potassium homeostasis through the mitochondrial K(+)/H(+) exchange regulation (PubMed:11907266, PubMed:15138253). With MBA1, plays a role in ribosomal translation and protein insertion into the inner membrane (PubMed:20427570). Interacts with MBA1. Binds to mitoribosomes in order to recruit them to the mitochondrial inner membrane. The matrix-exposed C-terminus contains a 14-3-3-like domain which is necessary and sufficient for interaction with mitochondrial ribosomes. Leads to the absence of respiratory complexes III and IV in mitochondrial inner membrane when MBA1 is also missing. Present with 7390 molecules/cell in log phase SD medium.