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. Functions as a spatio-temporal marker for assembly of contractile apparatus made of TssB1 and TssC1. This role in assembly depends on TssM1. Forms transient higher-order structures that correlated with dynamics of sheath component TssB1 (PubMed:31379775). Interacts with TssA1 (PubMed:27288401). Deletion mutant shows a severely reduced secretion of VgrG1a, VgrG1c as well as Hcp1.