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Phosphorylation site specificity of the CDC2-related kinase PITALRE
1Fels Institute for Cancer Research, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Abstract:
PITALRE is a human protein kinase belonging to the cell division cycle 2 (CDC2) kinase family, and is the catalytic subunit of a multimeric complex that contains several cellular proteins. PITALRE complexes from several cell lines and tissues phosphorylate retinoblastoma protein and myelin basic protein (MBP). In the present work, we have found that MBP is phosphorylated by PITALRE complexes on both Ser and Thr residues. Two different antibodies raised to PITALRE purified virtually identical kinase activities, as analysed by MBP phosphopeptide mapping and phosphoamino acid analysis. We have identified the proline-directed residue Ser-162 of MBP as a major phosphorylation site for PITALRE. In addition, our results suggest that one of the two MBP proline-directed threonine residues, Thr-97, is also selectively phosphorylated by PITALRE. These data, together with analysis of different peptide substrates derived from sites on MBP that are phosphorylated by PITALRE, indicate that PITALRE is a Ser/Thr proline-directed kinase. In addition, our results show that PITALRE has a substrate site specificity distinguishable from those of the CDC2 and cyclin-dependent kinase 2 (CDK2).
Insights
PITALRE, a human protein kinase, phosphorylates myelin basic protein (MBP) at specific Ser/Thr proline-directed residues. This kinase exhibits distinct substrate specificity compared to CDC2 and CDK2.
Area of Science:
- Molecular Biology
- Biochemistry
- Cell Signaling
Background:
- PITALRE is a human protein kinase and the catalytic subunit of a complex involved in cell division.
- PITALRE complexes phosphorylate key substrates like retinoblastoma protein and myelin basic protein (MBP).
Purpose of the Study:
- To characterize the phosphorylation sites and substrate specificity of PITALRE.
- To determine if PITALRE acts as a Ser/Thr proline-directed kinase.
- To compare PITALRE's specificity with related kinases like CDC2 and CDK2.
Main Methods:
- Phosphorylation assays using MBP and peptide substrates.
- Phosphopeptide mapping and phosphoamino acid analysis.
- Antibody purification of PITALRE kinase activity.
Main Results:
- MBP is phosphorylated by PITALRE on both Serine (Ser) and Threonine (Thr) residues.
- Ser-162 and Thr-97 of MBP were identified as major and selective phosphorylation sites for PITALRE.
- PITALRE was confirmed as a Ser/Thr proline-directed kinase with unique substrate specificity.
Conclusions:
- PITALRE is a novel Ser/Thr proline-directed kinase.
- PITALRE displays distinct substrate specificity compared to CDC2 and CDK2, suggesting unique roles in cellular processes.