{{Short description|Protein-coding gene in the species Homo sapiens}} {{Infobox_gene}} '''NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 5, 16kDa''' is a protein that in humans is encoded by the NDUFB5 gene.<ref name="entrez">{{cite web | title = Entrez Gene: NDUFB5 NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 5, 16kDa | url = https://www.ncbi.nlm.nih.gov/gene/4711 }}</ref> The NDUFB5 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.<ref name = Biochem>{{cite book | first1 = Donald | last1 = Voet | first2 = Judith G. | last2 = Voet | first3 = Charlotte W. | last3 = Pratt | name-list-style = vanc | author1-link = Donald Voet | author2-link = Judith G. Voet | title = Fundamentals of biochemistry: life at the molecular level | date = 2013 | publisher = Wiley | location = Hoboken, NJ | isbn = 978-0-470-54784-7 | chapter = Chapter 18 | pages = 581–620 | edition = 4th }}</ref>
==Structure==
The NDUFB5 gene, located on the q arm of chromosome 3 in position 26.33, is 19,713 base pairs long. The NDUFB5 protein weighs 21.7 kDa and is composed of 189 amino acids.<ref name=COPaKB>{{cite journal | vauthors = 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 | title = Integration of cardiac proteome biology and medicine by a specialized knowledgebase | journal = Circulation Research | volume = 113 | issue = 9 | pages = 1043–53 | date = Oct 2013 | pmid = 23965338 | pmc = 4076475 | doi = 10.1161/CIRCRESAHA.113.301151 }}</ref><ref name="url_COPaKB">{{cite web | url = https://amino.heartproteome.org/web/protein/O43674 | work = Cardiac Organellar Protein Atlas Knowledgebase (COPaKB) | title = NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 5 | access-date = 2018-07-18 | archive-date = 2018-07-21 | archive-url = https://web.archive.org/web/20180721025306/https://amino.heartproteome.org/web/protein/O43674 | url-status = dead }}</ref> NDUFB5 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.<ref name = "Biochem"/> NDUFB5 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.<ref name = "entrez" />
==Function==
The human NDUFB5 gene codes for a subunit of Complex I of the respiratory chain, which transfers electrons from NADH to ubiquinone.<ref name="entrez"/> However, NDUFB5 is an accessory subunit of the complex that is believed not to be involved in catalysis.<ref name = uniprot>{{cite web|title=NDUFB5 - NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 5|url=https://www.uniprot.org/uniprot/O43674|website=UniProt: a hub for protein information|publisher=The UniProt Consortium|accessdate=2 April 2015}}</ref> Initially, NADH binds to Complex I and transfers two electrons to the isoalloxazine ring of the flavin mononucleotide (FMN) prosthetic arm to form FMNH<sub>2</sub>. 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 (CoQH<sub>2</sub>). The flow of electrons changes the redox state of the protein, resulting in a conformational change and p''K'' shift of the ionizable side chain, which pumps four hydrogen ions out of the mitochondrial matrix.<ref name=Biochem />
==References== {{reflist}}
Category:Mitochondrial proteins