Previous studies have shown that the cyclin-dependent kinase (Cdk) inhibitor p27(Kip1) is targeted for degradation by an SCF(Skp2) ubiquitin ligase complex and that this process requires Cks1, a member of the highly conserved Suc1/Cks family of cell cycle regulatory proteins. All proteins of this family have Cdk-binding and anion-binding sites, but only mammalian Cks1 binds to Skp2 and promotes the association of Skp2 with p27 phosphorylated on Thr-187. The molecular mechanisms by which Cks1 promotes the interaction of the Skp2 ubiquitin ligase subunit to p27 remained obscure. Here we show that the Skp2-binding site of Cks1 is located on a region including the alpha2- and alpha1-helices and their immediate vicinity, well separated from the other two binding sites. All three binding sites of Cks1 are required for p27-ubiquitin ligation and for the association of Skp2 with Cdk-bound, Thr-187-phosphorylated p27. Cks1 and Skp2 mutually promote the binding of each other to a peptide similar to the 19 C-terminal amino acids of p27 containing phosphorylated Thr-187. This latter process requires the Skp2- and anion-binding sites of Cks1, but not its Cdk-binding site. It is proposed that the Skp2-Cks1 complex binds initially to the C-terminal region of phosphorylated p27 in a process promoted by the anion-binding site of Cks1. The interaction of Skp2 with the substrate is further strengthened by the association of the Cdk-binding site of Cks1 with Cdk2/cyclin E, to which phosphorylated p27 is bound. Study holds ProTherm entries: 15714, 15715, 15716, 15717, 15718, 15719, 15720, 15721, 15722, 15723, 15724, 15725, 15726, 15727, 15728, 15729, 15730, 15731, 15732, 15733 Extra Details: 1 mM EDTA was added in the experiment. protein folding; protein stability; transition state; topology; phi-values
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:46 p.m.
|Number of data points||79|
|Proteins||Cyclin-dependent kinases regulatory subunit 1 ; Cyclin-dependent kinases regulatory subunit 1|
|Assays/Quantities/Protocols||Experimental Assay: Cm ; Experimental Assay: m ; Experimental Assay: dG_H2O ; Derived Quantity: ddG_H2O|
|Libraries||Mutations for sequence MSHKQIYYSDKYDDEEFEYRHVMLPKDIAKLVPKTHLMSESEWRNLGVQQSQGWVHYMIHEPEPHILLFRRPLPKKPKK|