Component of the LUBAC complex which conjugates linear ('Met-1'-linked) polyubiquitin chains to substrates and plays a key role in NF-kappa-B activation and regulation of inflammation (By similarity). LUBAC conjugates linear polyubiquitin to ikbkg and RIPK1 and is involved in activation of the canonical NF-kappa-B and the JNK signaling pathways (By similarity). Linear ubiquitination mediated by the LUBAC complex interferes with TNF-induced cell death and thereby prevents inflammation (By similarity). LUBAC is recruited to the TNF-R1 signaling complex (TNF-RSC) to conjugate linear polyubiquitin to ikbkg and possibly other components contributing to the stability of the complex (By similarity). The LUBAC complex is also involved in innate immunity by conjugating linear polyubiquitin chains at the surface of bacteria invading the cytosol to form the ubiquitin coat surrounding bacteria (By similarity). LUBAC is not able to initiate formation of the bacterial ubiquitin coat, and can only promote formation of linear polyubiquitins on pre-existing ubiquitin (By similarity). The bacterial ubiquitin coat acts as an 'eat-me' signal for xenophagy and promotes NF-kappa-B activation (By similarity). Binds polyubiquitin of different linkage types (By similarity). [E2 ubiquitin-conjugating enzyme]-S-ubiquitinyl-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-N(6)-ubiquitinyl-L-lysine. Protein modification; protein ubiquitination. Component of the LUBAC complex (linear ubiquitin chain assembly complex). The RanBP2-type zinc finger, also called Npl4 zinc finger (NZF), mediates binding to 'Met-1'-linked polyubiquitins. The UBL domain mediates association with RNF31 via interaction with its UBA domain. Belongs to the RBR family.