Forms a proton-gated ion channel with pbo-5 that is activated by acidification of the posterior coelomic space, leading to posterior body wall muscle contraction (pBoc) during the defecation cycle. Not necessary for stimulation of posterior body contraction (pBoc). Does not bind neurotransmitters such as acetylcholine, gamma-aminobutyric acid, glycine, serotonin, glutamate or choline. The functional channel is a hetero-oligomer of pbo-5 and pbo-6. Expressed in the posterior body muscles. No visible phenotype. Mutants exhibit normal posterior body contractions. Belongs to the ligand-gated ion channel (TC 1.A.9) family. Acetylcholine receptor (TC 1.A.9.1) subfamily.