A protein complex that forms part of a proton-transporting V-type ATPase and mediates proton transport across a membrane. The V0 complex consists of at least four different subunits (a,c,d and e); six or more c subunits form a proton-binding rotor ring. [ https://www.worldcat.org/search?q=bn%3A0716743663 http://www.ncbi.nlm.nih.gov/pubmed/16449553 ]