Plays an essential role in the controlled expression of archaellum components during starvation-induced motility. May inhibit arnR transcription and promote ArnR translation. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Autophosphorylation is stimulated by Mn(2+). Induced during starvation conditions. Autophosphorylated. Deletion results in dysregulation of the archaellum regulatory network that leads to reduced motility, though the archaellum is properly assembled. Deletion mutant is still able to sense starvation and to induce archaellum formation, but with a delay at the signal transduction cascade level. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.