Acts as a spatial inhibitor of signaling that modulates abscission zone cell adhesion and expansion. Acts both directly and indirectly by physically interacting with RLK5/HAE and SOBIR1/EVR at the cell surface. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with SOBIR1/EVR and RLK5/HAE. Predominantly localized at the plasma membrane. A number of isoforms are produced. According to EST sequences. Autophosphorylated on serine, threonine and tyrosine residues. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. Was originally (PubMed:1851993) reported to be a connexin and to contain transmembrane domains. PubMed:8400879 authors have assigned that this is not a connexin, but rather a protein kinase. Sequencing errors.