To test our hypothesis that obscurin-kin1 modulates, at least in part, the mechanochemical coupling of cardiomyocytes via phosphorylation of N-cadherin, which has been shown to play a pivotal role in these processes, we set forth to identify the potential phosphorylation target sites of obscurin-kin1 within the cytoplasmic domain of N-cadherin. To this end, we used the baculovirus system to produce catalytically active kin1 coupled to 6xHis-tag (His-Kin1-CA) and the bacterial system to produce an N-cadherin construct containing a portion of the cytoplasmic domain (aa 786-880, accession no. P15116) tagged to 6xHis (His-Ncad786-880), which is enriched in Ser residues predicted to be potent phosphorylation target sites by EXPASY/GPS2.1. Following affinity purification of the recombinant proteins, His-Ncad786-880 was subjected to an in vitro kinase assay in the presence of His-Kin1-CA or control baculovirus preparation infected with empty vector that had undergone the same purification process as His-Kin1-CA. The reaction mixtures were subsequently subjected to liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. An N-cadherin peptide encompassing amino acids 786-807 containing a single phosphorylation event at Ser-788 was repeatedly identified in the His-Ncad786-880 reaction mixture when treated with His-Kin1-CA, but not in the control preparation