NDUFB2

NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 2, mitochondrial is an is_associated_with::enzyme that in humans is encoded by the NDUFB2 is_associated_with::gene. NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 2, 8kDa is an accessory subunit of the is_associated_with::NADH dehydrogenase (ubiquinone) complex, located in the is_associated_with::mitochondrial inner membrane. It is also known as is_associated_with::Complex I and is the largest of the five complexes of the is_associated_with::electron transport chain.

Structure
The NDUFB2 gene, located on the q arm of is_associated_with::chromosome 7 in position 34, is 9,966 base pairs long and is composed of 4 exons. The NDUFB2 protein weighs 8 kDa and is composed of 105 amino acids. NDUFB2 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. NDUFB3 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. Hydropathy analysis revealed that this subunit and 4 other subunits have an overall hydrophilic pattern, even though they are found within the hydrophobic protein (HP) fraction of complex I.

Function
The human NDUFB2 gene codes for a subunit of Complex I of the respiratory chain, which transfers electrons from NADH to is_associated_with::ubiquinone. However, NDUFB2 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.