Non-receptor tyrosine-protein kinase which plays a role in pharynx function by regulating pumping and the orientation of pharyngeal muscle fibers, independently of src-1 and src-2 (PubMed:19210548). May phosphorylate and thereby negatively regulate src-1 and src-2 activities (PubMed:12527374). ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Expressed predominantly in pharyngeal muscles in procorpus, metacorpus and terminal bulb (PubMed:12527374, PubMed:19210548). Expressed also in some neurons (ASE, ADF, AVA, AUA, RMDV and BAG) in the head region, anchor cell, vulva, cells around anus, body wall muscle and gondal distal tip cells (PubMed:12527374). Expressed mainly in the pharynx in the loop stage embryo. At L1 larval stage, predominantly expressed in the pharynx with some expression in body wall muscle, anchor cells and tail region. Belongs to the protein kinase superfamily. Tyr protein kinase family. CSK subfamily.