The Hop family consists of 31 outer membrane proteins in Helicobacter pylori. Five such proteins, HopA-HopE have been shown to function as porins both in bacterial outer membranes and in reconstituted planar bilayer membranes. The HopE protein appears to form a β-barrel with 16 transmembrane amphipathic β-strands. It is the smallest of the characterized Hop family members, but it forms the largest channels with a single channel conductance of 1.5 nS in 1M KCl.

The generalized transport reaction catalyzed by Hop family porins is:

solute (out) solute (periplasm)