Toxic component of a type II toxin-antitoxin (TA) system. Degrades total E.coli RNA, which is partially inhibited by cognate antitoxin VapB15 (PubMed:25450593). Upon expression in M.smegmatis inhibits colony formation, which is neutralized by coexpression with VapB15 (PubMed:20011113). The heterotrimer binds 1 Mg(2+)-Mn(2+) pair while the heterotetramer binds 2 pairs. Both metals are shared by the toxin-antitoxin pair. The heterotrimer binds 1 Mg(2+)-Mn(2+) pair while the heterotetramer binds 2 pairs. Both metals are shared by the toxin-antitoxin pair. RNase activity inhibited by EDTA. Crystallizes as a VapB15-VapC15(2) heterotrimer and as a VapB15(2)-VapC15(2) heterotetramer; each toxin pair forms a homodimer which creates a channel in which the antitoxin binds. Induced by hypoxia. In this enzyme the conserved residue Asp-4 binds Mg(2+) via H(2)O. Belongs to the PINc/VapC protein family.