A large protein complex, containing 12-15 subunits, that spans the cell envelope of Gram-negative bacteria and mediates the movement of proteins into the extracellular environment. The complex includes a component in the cytoplasm, an inner membrane subcomplex that reaches into the periplasmic compartment and a secretion pore in the outer membrane. Proteins using the Type II pathway are transported across the cytoplasmic membrane by the Sec or Tat complex.