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 (PubMed:1683466, PubMed:8416897, PubMed:11115123, PubMed:11994151, PubMed:17233825). The Tol-Pal system is also required for polar localization of chemoreceptors clusters (PubMed:24720726). The system also appears to be required for the activity of several outer membrane-localized enzymes with cell wall remodeling activity (PubMed:32152098). Is involved in the uptake of group A colicins (colicins A, E1, E2, E3, and K) and in the uptake of filamentous phage DNA (PubMed:1683466). 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 (PubMed:17233825). TolA interacts with TolQ and TolR via its N-terminal domain (PubMed:7744737, PubMed:10419942). Interacts with CpoB, and with the trimeric porins OmpC, OmpF, PhoE and LamB via its central domain (PubMed:8978668, PubMed:11994151). Interacts with TolB via its C-terminal domain (PubMed:11994151). Also interacts with Pal via its C-terminal domain. This interaction is proton motive force dependent and requires TolQ and TolR (PubMed:11115123, PubMed:11722743). Accumulates at cell constriction sites. Recruitment to the division site is dependent on FtsN activity. Contains an N-terminal domain that anchors the protein to the inner membrane, a central domain (domain II), and a C-terminal domain (domain III), which is the functional portion of the protein (PubMed:2068069). The C-terminal domain is involved in interaction with TolB and Pal, and is also involved in direct interaction with colicins and phages. It adapts its conformation upon binding to various partners (PubMed:11115123, PubMed:11994151, PubMed:15701516). Mutants lacking the tol-pal cluster suffer delayed outer membrane invagination and contain large outer membrane blebs at constriction sites and cell poles (PubMed:17233825). Tol-pal mutants fail to complete division and form cell chains, and fail to process denuded peptidoglycans at the septum (PubMed:32152098). Belongs to the TolA family.