Part of the H1 type VI secretion system (H1-T6SS) specialized secretion system, which delivers several virulence factors in both prokaryotic and eukaryotic cells during infection (PubMed:21325275, PubMed:24794869). Allows the delivery of the Tse5/RhsP1 toxin to target cells where it exerts its toxicity (PubMed:24794869). Forms homomultimers (PubMed:21325275). Part of the type VI secretion system (T6SS) (PubMed:21325275). Deletion of vgrG1c shows residual type VI secretion (PubMed:21325275). However, simultaneous deletion of all three vgrG genes (vgrG1a, vgrG1b and vgrG1c) totally abrogates bacterial killing (PubMed:24794869). Belongs to the VgrG protein family.