Mitochondrial acyl carrier protein (mtACP), also known as NADH:ubiquinone oxidoreductase subunit AB1 (NDUFAB1), is a protein encoded by the human NDUFAB1 gene. As a soluble matrix protein, it functions as a scaffold on which mitochondrial fatty acid synthesis (mtFAS) builds de novo fatty acyl chains. The octanoyl (C8) form of mtACP provides the precursor for mitochondrial lipoic acid biosynthesis, and protein–protein interactions between mtACP and LYRM proteins are required for central mitochondrial processes, including the assembly of respiratory chain complexes, iron–sulfur cluster biogenesis, and mitochondrial ribosome assembly. Through its binding to the complex I subunits LYRM3 and LYRM6, acyl-mtACP is incorporated as a structural component of complex I, giving rise to its designation as NDUFAB1.
mtFAS-derived acyl-mtACP and its interactions with LYRM proteins have been hypothesized to form a feedback loop that allows acetyl-CoA to regulate its own consumption through the assembly of respiratory chain complexes, which in turn controls citric acid cycle flux.