p13(SUC1) and the WW domain of PIN1 bind to the same phosphothreonine-proline epitope.
The WW domain of the human PIN1 and p13(SUC1), a subunit of the cyclin-dependent kinase complex, were previously shown to be involved in the regulation of the cyclin-dependent kinase complex activity at the entry into mitosis, by an unresolved molecular mechanism. We report here experimental evidence for the direct interaction of p13(SUC1) with a model CDC25 peptide, dependent on the phosphorylation state of its threonine. Chemical shift perturbation of backbone (1)H(N), (15)N, and (13)Calpha resonances during NMR titration experiments allows accurate identification of the binding site, primarily localized around the anion-binding site, occupied in the crystal structure of the homologous p9(CKSHs2) by a sulfate molecule. The epitope recognized by p13(SUC1) includes the proline at position +1 of the phosphothreonine, as was shown by the decrease in affinity for a mutated CDC25 phosphopeptide, containing an alanine/proline substitution. No direct interaction between the PIN1 WW domain or its catalytic proline cis/trans-isomerase domain and p13(SUC1) was detected, but our study showed that in vitro the WW domain of the human PIN1 antagonizes the binding of the p13(SUC1) to the CDC25 phosphopeptide, by binding to the same phosphoepitope. We thus propose that the full cyclin-dependent kinase complex stimulates the phosphorylation of CDC25 through binding of its p13(SUC1) module to the phosphoepitope of the substrate and that the reported WW antagonism of p13(SUC1)-stimulated CDC25 phosphorylation is caused by competitive binding of both protein modules to the same phosphoepitope.
Landrieu
I
I
CNRS UMR 8525, Institut de Biologie de Lille/Pasteur Institute of Lille, 59019 Lille Cedex, France. isabelle.landrieu@pasteur-lille.fr
Odaert
B
B
Wieruszeski
J M
JM
Drobecq
H
H
Rousselot-Pailley
P
P
Inze
D
D
Lippens
G
G
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000737:chemistry; D000939:Epitopes / Q000737:chemistry / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019906:Nuclear Magnetic Resonance, Biomolecular; D019696:Peptidylprolyl Isomerase / Q000737:chemistry* / Q000378:metabolism*; D010748:Phosphopeptides / Q000737:chemistry; D010769:Phosphothreonine / Q000378:metabolism*; D011392:Proline / Q000378:metabolism*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins; D014982:Xenopus laevis; D020666:ras-GRF1 / Q000737:chemistry
D018797:Cell Cycle Proteins; D000939:Epitopes; D005656:Fungal Proteins; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D010748:Phosphopeptides; D011994:Recombinant Proteins; D029702:Schizosaccharomyces pombe Proteins; C051655:Suc1 protein, S pombe; D020666:ras-GRF1; D010769:Phosphothreonine; D011392:Proline; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase