Core component of the H1 type VI (H1-T6SS) secretion system that plays a role in the release of toxins targeting both eukaryotic and prokaryotic species. Plays a role in correct elongation and stability of TssB1-sheath (PubMed:21873404, PubMed:22906320). Functions downstream of TssK1 and prevents detachment of TssB1-sheath and its premature disassembly. Once bound onto the sheath via an interaction with TssB1, provides an ideal docking point for ClpV1 to be recruited to the sheath (PubMed:31379775). Interacts with TssB1 (via N-terminus) (PubMed:22906320). Interacts with TssA1 (PubMed:27288401). Deletion mutant does not prevent TssB1 assembly into a sheath-like structure. However, the sheath exhibits an aberrant phenotype and break itself in smaller pieces.