Multi-site phosphorylation of Pho4 by the cyclin-CDK Pho80-Pho85 is semi-processive with site preference.
As part of a nutrient-responsive signaling pathway, the budding yeast cyclin-CDK complex Pho80-Pho85 phosphorylates the transcription factor Pho4 on five sites and inactivates it. Here, we describe the kinetic reaction between Pho80-Pho85 and Pho4. Through experimentation and computer modeling we have determined that Pho80-Pho85 phosphorylates Pho4 in a semi-processive fashion ... that results from a balance between kcat and k(off). In addition, we show that Pho80-Pho85 phosphorylates certain sites preferentially. Phosphorylation of the site with the highest preference inhibits the transcriptional activity of Pho4 when it is in the nucleus, while phosphorylation of the lowest-preference sites is required for export of Pho4 from the nucleus. This method of phosphorylation may allow Pho80-Pho85 to quickly inactivate Pho4 in the nucleus and efficiently phosphorylate Pho4 to completion.
Mesh Terms:
Binding Sites, Computer Simulation, Cyclin-Dependent Kinases, Cyclins, DNA-Binding Proteins, Dipeptides, Escherichia coli, Fungal Proteins, Mutation, Phosphorylation, Recombinant Proteins, Repressor Proteins, Saccharomyces cerevisiae Proteins, Substrate Specificity, Transcription Factors, Trypsin
Binding Sites, Computer Simulation, Cyclin-Dependent Kinases, Cyclins, DNA-Binding Proteins, Dipeptides, Escherichia coli, Fungal Proteins, Mutation, Phosphorylation, Recombinant Proteins, Repressor Proteins, Saccharomyces cerevisiae Proteins, Substrate Specificity, Transcription Factors, Trypsin
J. Mol. Biol.
Date: Mar. 09, 2001
PubMed ID: 11237614
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