Protein post-translational modification is a critical means for the organisms to regulate their activities (Wu, 2011). Among these modifications, protein phosphorylation may be the most important one that involves in the regulation of almost all biological functions. Protein kinases are the major enzymes that are responsible for the protein phosphorylation. On the other hand, protein kinases require other proteins as the partners to assist or facilitate their kinase activities. In this JMCB issue, four papers deliver new information for us to know more about the partners for protein kinases.