Composite low affinity interactions dictate recognition of the cyclin-dependent kinase inhibitor Sic1 by the SCF[superscript Cdc4] ubiquitin ligase
- HSC
The ubiquitin ligase SCF{sup Cdc4} (Skp1/Cul1/F-box protein) recognizes its substrate, the cyclin-dependent kinase inhibitor Sic1, in a multisite phosphorylation-dependent manner. Although short diphosphorylated peptides derived from Sic1 can bind to Cdc4 with high affinity, through systematic mutagenesis and quantitative biophysical analysis we show that individually weak, dispersed Sic1 phospho sites engage Cdc4 in a dynamic equilibrium. The affinities of individual phosphoepitopes serve to tune the overall phosphorylation site threshold needed for efficient recognition. Notably, phosphoepitope affinity for Cdc4 is dramatically weakened in the context of full-length Sic1, demonstrating the importance of regional environment on binding interactions. The multisite nature of the Sic1-Cdc4 interaction confers cooperative dependence on kinase activity for Sic1 recognition and ubiquitination under equilibrium reaction conditions. Composite dynamic interactions of low affinity sites may be a general mechanism to establish phosphorylation thresholds in biological responses.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- FOREIGN
- OSTI ID:
- 1036344
- Journal Information:
- Proc. Natl. Acad. Sci. USA, Vol. 109, Issue (9) ; 02, 2012; ISSN 0027-8424
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Structure/Function Implications in a Dynamic Complex of the Intrinsically Disordered Sic1 with the Cdc4 Subunit of an SCF Ubiquitin Ligase
Structural basis for phosphodependent substrate selection and orientation by the SCFCdc4 ubiquitin ligase