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The CDKs directly involved in the regulation of the cell cycle associate with small, 9- to 13-kiloDalton proteins called Suk1 or [[CKS1B|Cks]].<ref name = "Morgan1997" /> These proteins are required for CDK function, but their precise role is unknown.<ref name = "Morgan1997" />
Cks1 binds the carboxy lobe of the CDK, and recognizes phosphorylated residues. It may help the cyclin-CDK complex with substrates that have multiple phosphorylation sites by increasing affinity for the substrate.<ref name = "Morgan1997" />
=== Activadores das CDKs que non son ciclinas ===
===Non-cyclin= CDKCiclinas Activatorsvirais ====
Os [[virus]] poden codificar proteínas con [[homoloxía de secuencias]] coas ciclinas. Un exemplomoi estudado é a ciclina K (ou ciclina v) do [[herpesvirus]] do [[sarcma de Kaposi]], que activa CDK6. Os complexos ciclina viral-CDK teñen diferentes especificidades de substrato e sensibilidades de regulación.<ref name = "noncyclin">Nebreda, Angel R. (2006) “CDK activation by non-cyclin proteins.” “Current Opinion in Cell Biology.” 18:192-198</ref>
==== ViralActivdores Cyclinsde CDK5 ====
As proteínas p35 e p39 activan CDK5. Aínda que carecen de homoloxía de secuencias coas ciclinas, as estruturas cristalinas mostran que a p35 se prega dun modo similar ao das ciclinas. Con todo, a activación de CDK5 non require a fosforilación do bucle deactivación.<ref name = "noncyclin" />
Viruses can encode proteins with sequence homology to cyclins. One much-studied example is K-cyclin (or v-cyclin) from Kaposi sarcoma herpes virus (see [[Kaposi’s sarcoma]]), which activates CDK6. Viral cyclin-CDK complexes have different substrate specificities and regulation sensitivities.<ref name = "noncyclin">Nebreda, Angel R. (2006) “CDK activation by non-cyclin proteins.” “Current Opinion in Cell Biology.” 18:192-198</ref>
==== CDK5 Activators ====
The proteins p35 and p39 activate CDK5. Although they lack cyclin sequence homology, crystal structures show that p35 folds in a similar way as the cyclins. However, activation of CDK5 does not require activation loop phosphorylation.<ref name = "noncyclin" />
==== RINGO/Speedy ====
ProteinsProteínas withcon noningunha homologyhomoloxía tocoas theciclinas cyclinpoden familyser canactivadores bedirectos direct activators ofdas CDKs.<ref name = "ringo">Mouron, Silvana; de Carcer, Guillermo; Seco, Esther; Fernandez-Miranda, Gonzalo; Malumbres, Marcos; Nebreda, Angel. (2010). "RINGO C is required to sustain the spindle assembly checkpoint." ''Journal of Cell Science.'' 123:2586-2595.</ref> Unha Onefamilia familydeses ofactivadores suché activatorsa is thefamilia RINGO/Speedy family,<ref name = "ringo" /> whichque wasfoi originallydescuberta discoveredorixinalmente inen ''[[Xenopus]]''. AllOs cinco membros fivedescubertos membersata discoveredagora soactivan fartodos directlydirectamente activatea Cdk1 ande Cdk2, butpero theo complexo RINGO/Speedy-CDK2 complexrecoñece recognizesdiferentes differentsubstratos substratesque thano cyclincomplexo ciclina A-CDK2 complex.<ref name = "noncyclin" />
== Historia==
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