Cyclins are a family of proteins involved in the progression of cells through the cell cycle.
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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.[1][2]
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Cyclin, N-terminal domain
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| Identifiers | ||
| Symbol | Cyclin_N | |
| Pfam | PF00134 | |
| InterPro | IPR006671 | |
| SCOP | 1vin | |
| Available PDB structures:
1oiuB:181-307 1gy3B:181-307 1pkdD:181-307 1h1sD:181-307 1h27D:181-307 1oiyD:181-307 1h24D:181-307 1finB:181-307 1h1pD:181-307 1jstD:181-307 2c6tD:181-307 1vywD:181-307 1okvB:181-307 1h1qD:181-307 1oi9D:181-307 1h26B:181-307 1h28D:181-307 1p5eB:181-307 1h25B:181-307 2c4gD:181-307 1okwB:181-307 1fvvB:181-307 1jsuB:181-307 1e9hB:181-307 1urcD:181-307 1h1rD:181-307 1okuD:181-307 1qmzB:181-307 2bpmD:181-307 1oguB:181-307 1ol2D:181-307 1vin :179-305 1w98B:115-242 1xo2A:22-148 1jowA:22-148 1bu2A:22-148 1g3nG:20-147 1f5qB:19-145 1kxu :28-159 1jkw :28-159 1zp2A:10-134 |
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Cyclin, C-terminal domain
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| Identifiers | ||
| Symbol | Cyclin_C | |
| Pfam | PF02984 | |
| InterPro | IPR004367 | |
| Available PDB structures:
1oiuB:309-431 1gy3B:309-431 1pkdD:309-431 1h1sD:309-431 1h27D:309-431 1oiyD:309-431 1h24D:309-431 1finB:309-431 1h1pD:309-431 1jstD:309-431 2c6tD:309-431 1vywD:309-431 1okvB:309-431 1h1qD:309-431 1oi9D:309-431 1h26B:309-431 1h28D:309-431 1p5eB:309-431 1h25B:309-431 2c4gD:309-431 1okwB:309-431 1fvvB:309-431 1jsuB:309-431 1e9hB:309-431 1urcD:309-431 1h1rD:309-431 1okuD:309-431 1qmzB:309-431 2bpmD:309-431 1oguB:309-431 1ol2D:309-431 1vin :307-405 1w98B:244-370 |
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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.[3][4] Other specific types include:
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
- ^ Bai C, Richman R, Elledge SJ (1994). "Human cyclin F". EMBO J. 13 (24): 6087-98. PMID 7813445.
- ^ Kong M, Barnes EA, Ollendorff V, Donoghue DJ (2000). "Cyclin F regulates the nuclear localization of cyclin B1 through a cyclin-cyclin interaction". EMBO J. 19 (6): 1378-88. doi:10.1093/emboj/19.6.1378. PMID 10716937.
- ^ Fung TK, Poon RY (2005). "A roller coaster ride with the mitotic cyclins". Semin. Cell Dev. Biol. 16 (3): 335-42. doi:10.1016/j.semcdb.2005.02.014. PMID 15840442.
- ^ Gerald Karp,. Cell and Molecular Biology: Concepts and Experiments. New York: Wiley, 148, 165-170, and 624-664. ISBN 0-470-04217-6.
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| Cyclin | A - B - D - E |
| Cyclin-dependent kinase | 2 - 4 - 6 - 9 - CDK-activating kinase |
| Cyclin-dependent kinase inhibitor protein | p14arf/p16INK4a - p21 - p27 - p57 |
| Other | Cdc2 - Cdc25 - Cdc42 - Cellular apoptosis susceptibility protein - E2F - Maturation promoting factor - Wee |
Cyclin/CDK complexes controlling cell cycle Cyclin B/CDK1-regulates transmission from G2 to M 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 S phase.
