Cyclin
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robot Removing: [[nl:Cycline]]
[[Image:Cyclinexpression waehrend Zellzyklus.png|thumb|422px|Expression of cyclins through the [[cell cycle]].]]
'''Cyclins''' are a family of [[protein]]s involved in the progression of cells through the [[cell cycle]]. They are the "regulatory subunits of the heterodimeric protein kinases that control cell cycle events."{{Fact|date=April 2008}}
==Function==
A cyclin forms a complex with its partner [[cyclin-dependent kinase]] (Cdk), which activates the latter's [[protein kinase]] function.
Cyclins are so named because their concentration varies in a cyclical fashion during the cell cycle; they are produced or degraded as needed in order to drive the cell through the different stages of the cell cycle.
When its concentrations in the cell are low, the cyclin detaches from the Cdk, inhibiting the enzyme's activity, probably by causing a protein chain to block the enzymatic site.<ref name="pmid7813445">{{cite journal |author=Bai C, Richman R, Elledge SJ |title=Human cyclin F |journal=EMBO J. |volume=13 |issue=24 |pages=6087–98 |year=1994 |pmid=7813445 |doi=}}</ref><ref name="pmid10716937">{{cite journal |author=Kong M, Barnes EA, Ollendorff V, Donoghue DJ |title=Cyclin F regulates the nuclear localization of cyclin B1 through a cyclin-cyclin interaction |journal=EMBO J. |volume=19 |issue=6 |pages=1378–88 |year=2000 |pmid=10716937 |doi=10.1093/emboj/19.6.1378}}</ref>
{{Pfam_box
| Symbol = Cyclin_N
| Name = Cyclin, N-terminal domain
| image =
| width =
| caption =
| Pfam= PF00134
| InterPro= IPR006671
| SMART=
| PROSITE= PDOC00264
| SCOP = 1vin
| TCDB =
| OPM family=
| OPM protein=
| PDB=
{{PDB3|1oiu}}B:181-307 {{PDB3|1gy3}}B:181-307 {{PDB3|1pkd}}D:181-307
{{PDB3|1h1s}}D:181-307 {{PDB3|1h27}}D:181-307 {{PDB3|1oiy}}D:181-307
{{PDB3|1h24}}D:181-307 {{PDB3|1fin}}B:181-307 {{PDB3|1h1p}}D:181-307
{{PDB3|1jst}}D:181-307 {{PDB3|2c6t}}D:181-307 {{PDB3|1vyw}}D:181-307
{{PDB3|1okv}}B:181-307 {{PDB3|1h1q}}D:181-307 {{PDB3|1oi9}}D:181-307
{{PDB3|1h26}}B:181-307 {{PDB3|1h28}}D:181-307 {{PDB3|1p5e}}B:181-307
{{PDB3|1h25}}B:181-307 {{PDB3|2c4g}}D:181-307 {{PDB3|1okw}}B:181-307
{{PDB3|1fvv}}B:181-307 {{PDB3|1jsu}}B:181-307 {{PDB3|1e9h}}B:181-307
{{PDB3|1urc}}D:181-307 {{PDB3|1h1r}}D:181-307 {{PDB3|1oku}}D:181-307
{{PDB3|1qmz}}B:181-307 {{PDB3|2bpm}}D:181-307 {{PDB3|1ogu}}B:181-307
{{PDB3|1ol2}}D:181-307 {{PDB3|1vin}} :179-305 {{PDB3|1w98}}B:115-242
{{PDB3|1xo2}}A:22-148 {{PDB3|1jow}}A:22-148 {{PDB3|1bu2}}A:22-148
{{PDB3|1g3n}}G:20-147 {{PDB3|1f5q}}B:19-145 {{PDB3|1kxu}} :28-159
{{PDB3|1jkw}} :28-159 {{PDB3|1zp2}}A:10-134
}}
{{Pfam_box
| Symbol = Cyclin_C
| Name = Cyclin, C-terminal domain
| image =
| width =
| caption =
| Pfam= PF02984
| InterPro= IPR004367
| SMART=
| Prosite = PDOC00264
| SCOP =
| TCDB =
| OPM family=
| OPM protein=
| PDB=
{{PDB3|1oiu}}B:309-431 {{PDB3|1gy3}}B:309-431 {{PDB3|1pkd}}D:309-431
{{PDB3|1h1s}}D:309-431 {{PDB3|1h27}}D:309-431 {{PDB3|1oiy}}D:309-431
{{PDB3|1h24}}D:309-431 {{PDB3|1fin}}B:309-431 {{PDB3|1h1p}}D:309-431
{{PDB3|1jst}}D:309-431 {{PDB3|2c6t}}D:309-431 {{PDB3|1vyw}}D:309-431
{{PDB3|1okv}}B:309-431 {{PDB3|1h1q}}D:309-431 {{PDB3|1oi9}}D:309-431
{{PDB3|1h26}}B:309-431 {{PDB3|1h28}}D:309-431 {{PDB3|1p5e}}B:309-431
{{PDB3|1h25}}B:309-431 {{PDB3|2c4g}}D:309-431 {{PDB3|1okw}}B:309-431
{{PDB3|1fvv}}B:309-431 {{PDB3|1jsu}}B:309-431 {{PDB3|1e9h}}B:309-431
{{PDB3|1urc}}D:309-431 {{PDB3|1h1r}}D:309-431 {{PDB3|1oku}}D:309-431
{{PDB3|1qmz}}B:309-431 {{PDB3|2bpm}}D:309-431 {{PDB3|1ogu}}B:309-431
{{PDB3|1ol2}}D:309-431 {{PDB3|1vin}} :307-405 {{PDB3|1w98}}B:244-370
}}
==Types==
There are several different cyclins which are active in different parts of the cell cycle and which cause the Cdk to phosphorylate different substrates. However, there are several "orphan" cyclins for which no Cdk partner has been identified. For example, cyclin F is an orphan cyclin that is essential for G2/M transition.<ref name="pmid15840442">{{cite journal |author=Fung TK, Poon RY |title=A roller coaster ride with the mitotic cyclins |journal=Semin. Cell Dev. Biol. |volume=16 |issue=3 |pages=335–42 |year=2005 |pmid=15840442 |doi=10.1016/j.semcdb.2005.02.014}}</ref><ref name="isbn0-470-04217-6">{{cite book |author=Gerald Karp, |title=Cell and Molecular Biology: Concepts and Experiments |publisher=Wiley |location=New York |year= |pages= 148, 165-170, and 624-664|isbn=0-470-04217-6 |oclc= |doi=}}</ref>
Other specific types include:
* [[Cyclin D]]
* [[Cyclin E]]
* [[Cyclin A]]
* [[Cyclin B]]
==Domain structure==
Cyclins contain two domains of similar all-alpha fold, N- and C-terminal.
==Human proteins with cyclin domains ==
[[CABLES2]]; [[CCNA1]]; [[CCNA2]]; [[CCNB1]]; [[CCNB2]]; [[CCNB3]]; [[CCNC]]; [[CCND1]];
[[CCND2]]; [[CCND3]]; [[CCNE1]]; [[CCNE2]]; [[CCNF]]; [[CCNG1]]; [[CCNG2]]; [[CCNH]];
[[CCNI]]; [[CCNJ]]; [[CCNJL]]; [[CCNK]]; [[CCNL1]]; [[CCNT1]]; [[CCNT2]]; [[CCNY]];
[[CCNYL1]]; [[CNTD2]]; [[UDG2]];
==History==
[[Leland H. Hartwell]], [[R. Timothy Hunt]], and [[Paul M. Nurse]] won the 2001 [[Nobel Prize in Physiology or Medicine]] for their discovery of cyclin and cyclin-dependent kinase, central molecules in the regulation of the cell cycle.
== References ==
{{Reflist|2}}
*Lodish,Berk, Matsudaira, Kaiser, Kreiger, Scott, Zipursky & Darnell,Molecular Cell Biology, 5th edition
{{Cell cycle proteins}}
Cyclin/CDK complexes controlling cell cycle
Cyclin B/CDK1-regulates transmission from S to G2 phase.
Cyclin D/CDK4;Cyclin d/CDK 6;Cyclin E/CDK2-regulates transition from G1 to S phase.
Cyclin A/CDK2 and Cyclin B/CDK1-active in G1 phase.
[[Category:Cell cycle]]
[[Category:Proteins]]
[[de:Cyclin]]
[[es:Ciclina]]
[[fr:Cyclines (protéines)]]
[[it:Ciclina]]
[[hu:Ciklin]]
[[ja:サイクリン]]
[[pl:Cykliny]]
[[ru:Циклин]]
[[fi:Sykliini]]