Inner membrane component of the type II secretion system required for the energy-dependent secretion of extracellular factors such as proteases and toxins from the periplasm. Plays a role in the complex assembly and recruits GspM resulting in a stable complex in the inner membrane. Provides thus a link between the energy-providing GspE protein in the cytoplasm and the rest of the T2SS machinery. Type II secretion system is composed of four main components: the outer membrane complex, the inner membrane complex, the cytoplasmic secretion ATPase and the periplasm-spanning pseudopilus (By similarity). Forms homodimers. Interacts with GspM. Interacts with GspE and GspF (By similarity). Silenced by the DNA-binding protein H-NS under standard growth conditions. Part of a cryptic operon that encodes proteins involved in type II secretion machinery in other organisms, but is not expressed in strain K12. Belongs to the GSP L family. Extended N-terminus.