The human NDUFA5 gene codes for the B13 subunit of complex I of the respiratory chain, which transfers electrons from NADH to ubiquinone. The high degree of conservation of NDUFA5 extending to plants and fungi indicates its functional significance in the enzyme complex. The protein localizes to the inner mitochondrial membrane as part of the 7 component-containing, water soluble "iron-sulfur protein" (IP) fraction of complex I, although its specific role is unknown. It is assumed to undergo post-translational removal of the initiator methionine and N-acetylation of the next amino acid. The predicted secondary structure is primarily alpha helix, but the carboxy-terminal half of the protein has high potential to adopt a coiled-coil form. The amino-terminal part contains a putative beta sheet rich in hydrophobic amino acids that may serve as mitochondrial import signal. Several transcript variants encoding different isoforms have been found for this gene. Related pseudogenes have also been identified on four other chromosomes. [provided by RefSeq, Sep 2013]