NDUFB4

NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 4, 15kDa
Identifiers
Aliases	NDUFB4, B15, CI-B15
External IDs	MGI: 3782046 HomoloGene: 3342 GeneCards: 4710
Gene ontology Molecular function • NADH dehydrogenase (ubiquinone) activity Cellular component • integral component of membrane • mitochondrial inner membrane • mitochondrial respiratory chain complex I • respiratory chain • nuclear membrane • extracellular exosome • membrane • mitochondrion • nucleoplasm Biological process • respiratory electron transport chain • cellular metabolic process • oxidation-reduction process • response to oxidative stress • small molecule metabolic process • mitochondrial electron transport, NADH to ubiquinone • mitochondrial respiratory chain complex I assembly Sources:Amigo / QuickGO
Orthologs
Species	Human	Mouse
Entrez	4710	100042503
Ensembl	ENSG00000065518	ENSMUSG00000022820
UniProt	O95168	Q9CQC7
RefSeq (mRNA)	NM_004547 NM_001168331	XM_001478443
RefSeq (protein)	NP_001161803.1 NP_004538.2	NP_080886.1 XP_001476621.1 XP_001478493.1
Location (UCSC)	Chr 3: 120.6 – 120.6 Mb	Chr 16: 37.65 – 37.65 Mb
PubMed search
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NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 4, 15kDa is a protein that in humans is encoded by the NDUFB4 gene.^[1] The NDUFB4 protein is a subunit of NADH dehydrogenase (ubiquinone), which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain.^[2]

Structure

The NDUFB4 gene, located on the q arm of chromosome 3 in position 13.33, is 6,130 base pairs long. The NDUFB4 protein weighs 15 kDa and is composed of 129 amino acids.^[3][4] NDUFB4 is a subunit of the enzyme NADH dehydrogenase (ubiquinone), the largest of the respiratory complexes. The structure is L-shaped with a long, hydrophobic transmembrane domain and a hydrophilic domain for the peripheral arm that includes all the known redox centers and the NADH binding site.^[2] NDUFB4 is one of about 31 hydrophobic subunits that form the transmembrane region of Complex I and is of the non-catalytic subunits of the complex. It has been noted that the N-terminal hydrophobic domain has the potential to be folded into an 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 NADH dehydrogenase (ubiquinone) complex at the inner mitochondrial membrane.^[1]

Function

The human NDUFB4 gene codes for a subunit of Complex I of the respiratory chain, which transfers electrons from NADH to ubiquinone.^[1] However, NDUFB4 is an accessory subunit of the complex that is believed not to be involved in catalysis.^[5] Mammalian complex I is composed of 45 different subunits. It locates at the mitochondrial inner membrane. This protein complex has NADH dehydrogenase activity and oxidoreductase activity. It transfers electrons from NADH to the respiratory chain. The immediate electron acceptor for the enzyme is believed to be ubiquinone.^[1] Initially, NADH binds to Complex I and transfers two electrons to the isoalloxazine ring of the 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 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.^[2]

References

1. "Entrez Gene: NDUFB4 NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 4, 15kDa [ Homo sapiens (human) ]".
2. Voet D, Voet JG, Pratt CW (2013). "Chapter 18". Fundamentals of biochemistry: life at the molecular level (4th ed.). Hoboken, NJ: Wiley. pp. 581–620. ISBN 978-0-470-54784-7.
3. Zong NC, Li H, Li H, Lam MP, Jimenez RC, Kim CS, Deng N, Kim AK, Choi JH, Zelaya I, Liem D, Meyer D, Odeberg J, Fang C, Lu HJ, Xu T, Weiss J, Duan H, Uhlen M, Yates JR, Apweiler R, Ge J, Hermjakob H, Ping P (Oct 2013). "Integration of cardiac proteome biology and medicine by a specialized knowledgebase". Circulation Research 113 (9): 1043–53. doi:10.1161/CIRCRESAHA.113.301151. PMC 4076475. PMID 23965338.
4. "NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 4". Cardiac Organellar Protein Atlas Knowledgebase (COPaKB).
5. "NDUFB4 - NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 4". UniProt: a hub for protein information. The UniProt Consortium. Retrieved 2 April 2015.