May contribute to coordination of muscle contraction as regulatory subunit of a nonessential potassium channel complex. May form a complex with sup-9 and unc-93 where sup-10 and unc-93 act as regulatory subunits of the two pore potassium channel sup-9. Sup-10 may regulate sup-9 via sup-18. In body-wall muscle cells, localizes to dense body-like structure which connect the myofibril lattice to the cell membrane. Colocalizes with sup-18. Low levels in body-wall muscles, eight vulval muscles, intestinal muscles and anal depressor muscle. Gain of function uncoordinated rubber band response is phenocopied by exposure to the unc-49 agonist muscimol.