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. Forms a stable complex with TssB1. This complex, although not crucial for the H1-T6SS function, may fine-tune the assembly of the system (PubMed:22906320). Plays a role in the interaction between ClpV1 and the TssC1/TssB1 sheath (PubMed:25305017). Interacts with TssB1 (via N-terminus) (PubMed:22906320, PubMed:25305017). Interacts with ClpV1 (PubMed:25305017). Deletion has no detectable effect on the T6SS-mediated secretion of VgrG1a/c, Hcp1 or Tse3. The T6SS protein TagJ/HsiE1 is unique to the H1-T6SS and absent from the H2- and H3-T6SSs.