NDUFAB1

NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 5, 16kDa is a is_associated_with::protein that in humans is encoded by the NDUFAB1 is_associated_with::gene. The NDUFAB1 protein is a subunit of is_associated_with::NADH dehydrogenase (ubiquinone), which is located in the is_associated_with::mitochondrial inner membrane and is the largest of the five complexes of the is_associated_with::electron transport chain.

Structure
The NDUFAB1 gene is located on the p arm of is_associated_with::chromosome 16 at position 12.2 and it spans 15,327 base pairs. The NDUFAB1 gene produces a 17.4 kDa protein composed of 156 is_associated_with::amino acids. NDUFAB1 is a subunit of the enzyme is_associated_with::NADH dehydrogenase (ubiquinone), the largest of the respiratory complexes. The structure is L-shaped with a long, is_associated_with::hydrophobic is_associated_with::transmembrane domain and a is_associated_with::hydrophilic domain for the peripheral arm that includes all the known redox centers and the NADH binding site. NDUFAB1 is one of about 31 hydrophobic subunits that form the transmembrane region of Complex I. It has been noted that the N-terminal hydrophobic domain has the potential to be folded into an is_associated_with::alpha helix spanning the inner mitochondrial membrane with a C-terminal hydrophilic domain interacting with globular subunits of Complex I. The highly conserved two-domain structure suggests that this feature is critical for the protein function and that the hydrophobic domain acts as an anchor for the is_associated_with::NADH dehydrogenase (ubiquinone) complex at the inner mitochondrial membrane.

Function
The human NDUFAB1 gene codes for a subunit of Complex I of the respiratory chain, which transfers electrons from NADH to is_associated_with::ubiquinone. However, NDUFAB1 is an accessory subunit of the complex that is believed not to be involved in catalysis. Initially, is_associated_with::NADH binds to Complex I and transfers two electrons to the is_associated_with::isoalloxazine ring of the is_associated_with::flavin mononucleotide (FMN) prosthetic arm to form FMNH2. The electrons are transferred through a series of iron-sulfur (Fe-S) clusters in the prosthetic arm and finally to coenzyme Q10 (CoQ), which is reduced to is_associated_with::ubiquinol (CoQH2). The flow of electrons changes the redox state of the protein, resulting in a conformational change and pK shift of the ionizable side chain, which pumps four hydrogen ions out of the mitochondrial matrix.