Essential for mitochondrial network organization, mitochondrial metabolism and cell growth at organism and cellular level. May play an important role in mitochondrial protein synthesis. May also participate in mitochondrial DNA replication. May bind to mitochondrial DNA D-loops and contribute to nucleoid stability. Required for enhanced channeling of cholesterol for hormone-dependent steroidogenesis. Involved in mitochondrial-mediated antiviral innate immunity. Can form homooligomers. Homodimer formation at the N-terminus may be regulated by ATP and is required for the interaction with the inner surface of the mitochondrial outer membrane and correct mitochondrial homeostasis. Interacts with components of the mitochondrial ribosome and with other proteins involved in mitochondrial RNA metabolism. May also interact with protein involved in lipid metabolism, including STARD9. May interact with FAM210A. Interacts with GADD45GIP1. Interacts with HSP60/HSPD1. Forms heterooligomers with ATAD3B; this interaction may affect ATAD3A activity (By similarity). Interacts with S100B in a Ca(+2)- and Zn(+2)-dependent manner; this interaction probably occurs in the cytosol prior to mitochondrial targeting. S100B could assist ATAD3A cytoplasmic processing, preventing aggregation and favoring mitochondrial localization (PubMed:20351179). Interacts with CLPB (By similarity). Lacks a canonical N-terminal mitochondrial targeting signal. Has been shown to be very tightly associated with mitochondrial inner membrane. The N-terminus being either exposed to the cytosol or located in an accessible intermembrane space. Exposure to the cytosol would imply a second transmembrane that could not be predicted. The C-terminus is facing the matrix. In the matrix, may be associated with nucleoids (By similarity). Up-regulated during oligodendrocyte progenitor cell differentiation. The transmembrane domain and a C-terminal adjacent region contain all information necessary for mitochondrial targeting. Belongs to the AAA ATPase family.