Part of the Tol-Pal system, which plays a role in outer membrane invagination during cell division and is important for maintaining outer membrane integrity. The Tol-Pal system is composed of five core proteins: the inner membrane proteins TolA, TolQ and TolR, the periplasmic protein TolB and the outer membrane protein Pal. They form a network linking the inner and outer membranes and the peptidoglycan layer. Belongs to the ExbB/TolQ family.