Regulator of muscle contraction and relaxation. Senses mechanical strain that occurs during muscle activity by unfolding in clearly resolvable steps at differing forces (PubMed:18390597, PubMed:7190524). Plays a role in the organization of sarcomeres in body wall muscles (PubMed:25851606). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Forces generated by the contraction/relaxation cycles of muscle activity separate the regulatory domain from the catalytic core, activating the enzyme. At rest, the kinase domain is in a closed conformation. The active site is occupied by the autoinhibitory region (CDR), which makes extensive contact with the catalytic site, blocking substrate binding. At low forces the regulatory tail will unravel reversibly and expose the active site to its substrates, potentially stabilized by binding of Ca/CALM. At high forces the kinase begins to unfold and the integrity of the active site is disrupted. May interact (via protein kinase and CRD domains) with mak-1 (via protein kinase domain). Expressed at the outer edge of A-bands. Expressed in body wall, anal, vulval, and pharyngeal muscles (at protein level). Phosphorylated by mak-1 on the protein kinase domain and/or CDR domain in vitro. Body muscles are unable to develop or sustain normal contractions but small regions within the myofilament lattice of individual muscle cells contract transiently in the absence of contraction of the adjacent lattice (PubMed:16765996, PubMed:7190524). This results in a nearly constant body twitching phenotype (PubMed:16765996, PubMed:7190524, PubMed:25851606). Resistant to nicotine-induced paralysis (PubMed:25851606). Determination of the mutation frequency of the unc-22 gene has been used to study the biological effects of short duration spaceflight. Belongs to the protein kinase superfamily. CAMK Ser/Thr protein kinase family.