EIF5B

{{Short description|Protein-coding gene in the species Homo sapiens}} {{cs1 config|name-list-style=vanc|display-authors=6}} {{Infobox_gene}} '''Eukaryotic translation initiation factor 5B''' is a protein that in humans is encoded by the ''EIF5B'' gene.<ref name="Lee_1999">{{cite journal | vauthors = Lee JH, Choi SK, Roll-Mecak A, Burley SK, Dever TE | title = Universal conservation in translation initiation revealed by human and archaeal homologs of bacterial translation initiation factor IF2 | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 96 | issue = 8 | pages = 4342–4347 | date = April 1999 | pmid = 10200264 | pmc = 16334 | doi = 10.1073/pnas.96.8.4342 | doi-access = free | bibcode = 1999PNAS...96.4342L }}</ref><ref name="Wilson_1999">{{cite journal | vauthors = Wilson SA, Sieiro-Vazquez C, Edwards NJ, Iourin O, Byles ED, Kotsopoulou E, Adamson CS, Kingsman SM, Kingsman AJ, Martin-Rendon E | title = Cloning and characterization of hIF2, a human homologue of bacterial translation initiation factor 2, and its interaction with HIV-1 matrix | journal = The Biochemical Journal | volume = 342 ( Pt 1) | issue = Pt 1 | pages = 97–103 | date = August 1999 | pmid = 10432305 | pmc = 1220441 | doi = 10.1042/bj3420097 | series = 342 }}</ref><ref name="entrez">{{cite web | title = Entrez Gene: EIF5B eukaryotic translation initiation factor 5B | url = https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=ShowDetailView&TermToSearch=9669 }}</ref> eIF5B is homologous to the bacterial initiation factor 2, sharing a core structure while their involvement in translation initiation differs.<ref>{{cite journal | vauthors = Unbehaun A, Marintchev A, Lomakin IB, Didenko T, Wagner G, Hellen CU, Pestova TV | title = Position of eukaryotic initiation factor eIF5B on the 80S ribosome mapped by directed hydroxyl radical probing | journal = The EMBO Journal | volume = 26 | issue = 13 | pages = 3109–3123 | date = July 2007 | pmid = 17568775 | pmc = 1914099 | doi = 10.1038/sj.emboj.7601751 }}</ref>

== Function == {{see also|Eukaryotic translation#Cap-dependent initiation}} eIF5B plays an important role in later stages of the translation initiation mechanism. After the start codon has been engaged by the scanning initiation complex, eukaryotic initiation factors eIF1, eIF2, and eIF5 leave the ribosome. Subsequently, eIF5B-GTP is recruited to the ribosome. eIF1A induces rotation of a domain of eIF5B-GTP, which in turn positions the initiator tRNA such that joining of the large ribosomal subunit is possible.<ref>{{cite journal | vauthors = Lapointe CP, Grosely R, Sokabe M, Alvarado C, Wang J, Montabana E, Villa N, Shin BS, Dever TE, Fraser CS, Fernández IS, Puglisi JD | title = eIF5B and eIF1A reorient initiator tRNA to allow ribosomal subunit joining | journal = Nature | volume = 607 | issue = 7917 | pages = 185–190 | date = July 2022 | pmid = 35732735 | pmc = 9728550 | doi = 10.1038/s41586-022-04858-z | bibcode = 2022Natur.607..185L }}</ref> Joining of the large subunit causes hydrolysis of the eIF5B-bound GTP, which accelerates the release of eIF1A from the ribosome.<ref>{{cite journal | vauthors = Fringer JM, Acker MG, Fekete CA, Lorsch JR, Dever TE | title = Coupled release of eukaryotic translation initiation factors 5B and 1A from 80S ribosomes following subunit joining | journal = Molecular and Cellular Biology | volume = 27 | issue = 6 | pages = 2384–2397 | date = March 2007 | pmid = 17242201 | pmc = 1820483 | doi = 10.1128/MCB.02254-06 }}</ref> Dissociation of eIF1A leads to another rearrangement of eIF5B, placing the initiator tRNA in its final position.<ref>{{cite journal | vauthors = Wang J, Wang J, Shin BS, Kim JR, Dever TE, Puglisi JD, Fernández IS | title = Structural basis for the transition from translation initiation to elongation by an 80S-eIF5B complex | journal = Nature Communications | volume = 11 | issue = 1 | date = October 2020 | pmid = 33024099 | pmc = 7538418 | doi = 10.1038/s41467-020-18829-3 | bibcode = 2020NatCo..11.5003W | article-number = 5003 }}</ref> The hydrolysis of eIF5B's GTP reduces its affinity to the ribosome, ultimately leading to its dissociation. This concludes the initiation of translation.

== References == {{reflist}}

== Further reading == {{refbegin | 2}} * ''A comprehensive review on eukaryotic translation initiation'': {{cite journal | vauthors = Brito Querido J, Díaz-López I, Ramakrishnan V | title = The molecular basis of translation initiation and its regulation in eukaryotes | journal = Nature Reviews. Molecular Cell Biology | volume = 25 | issue = 3 | pages = 168–186 | date = March 2024 | pmid = 38052923 | doi = 10.1038/s41580-023-00624-9 }} * ''The structure of an 80S-eIF5B complex'': {{cite journal | vauthors = Wang J, Wang J, Shin BS, Kim JR, Dever TE, Puglisi JD, Fernández IS | title = Structural basis for the transition from translation initiation to elongation by an 80S-eIF5B complex | journal = Nature Communications | volume = 11 | issue = 1 | date = October 2020 | pmid = 33024099 | pmc = 7538418 | doi = 10.1038/s41467-020-18829-3 | bibcode = 2020NatCo..11.5003W | article-number = 5003 }} * {{cite journal | vauthors = Marintchev A, Kolupaeva VG, Pestova TV, Wagner G | title = Mapping the binding interface between human eukaryotic initiation factors 1A and 5B: a new interaction between old partners | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 100 | issue = 4 | pages = 1535–1540 | date = February 2003 | pmid = 12569173 | pmc = 149867 | doi = 10.1073/pnas.0437845100 | doi-access = free | bibcode = 2003PNAS..100.1535M }} * {{cite journal | vauthors = Olsen DS, Savner EM, Mathew A, Zhang F, Krishnamoorthy T, Phan L, Hinnebusch AG | title = Domains of eIF1A that mediate binding to eIF2, eIF3 and eIF5B and promote ternary complex recruitment in vivo | journal = The EMBO Journal | volume = 22 | issue = 2 | pages = 193–204 | date = January 2003 | pmid = 12514125 | pmc = 140105 | doi = 10.1093/emboj/cdg030 }} {{refend}}