Stereospecific Phosphorylation by the Central Mitotic Kinase Cdk1-Cyclin B

Abstract

The <i>cis</i> vs <i>trans</i> conformation, or shape, of phosphoserine-proline (pSer-Pro), a prevalent motif in cell cycle proteins, may play a significant role in regulating mitosis. We demonstrate that Cdk1-cyclin B, the central mitotic kinase, is specific for the <i>trans</i> conformation, not <i>cis</i>, of synthetic, locked Ser-Pro 11-residue peptide substrates, using LC-MSMS detection and sequencing of phosphorylated products. This substrate stereospecificity may contribute an additional level of mitotic regulation