E3 ubiquitin-protein ligase 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 (PubMed:17006537, PubMed:19136968, PubMed:20005846, PubMed:21455173, PubMed:21455180, PubMed:21455181, PubMed:22863777, PubMed:28481331, PubMed:28189684). LUBAC conjugates linear polyubiquitin to IKBKG and RIPK1 and is involved in activation of the canonical NF-kappa-B and the JNK signaling pathways (PubMed:17006537, PubMed:19136968, PubMed:20005846, PubMed:21455173, PubMed:21455180, PubMed:21455181, PubMed:22863777, PubMed:28189684). Linear ubiquitination mediated by the LUBAC complex interferes with TNF-induced cell death and thereby prevents inflammation (PubMed:21455173, PubMed:28189684). LUBAC is recruited to the TNF-R1 signaling complex (TNF-RSC) following polyubiquitination of TNF-RSC components by BIRC2 and/or BIRC3 and to conjugate linear polyubiquitin to IKBKG and possibly other components contributing to the stability of the complex (PubMed:20005846, PubMed:27458237). 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 (PubMed:28481331, PubMed:34012115). LUBAC is not able to initiate formation of the bacterial ubiquitin coat, and can only promote formation of linear polyubiquitins on pre-existing ubiquitin (PubMed:28481331). Recruited to the surface of bacteria by RNF213, which initiates the bacterial ubiquitin coat (PubMed:34012115). The bacterial ubiquitin coat acts as an 'eat-me' signal for xenophagy and promotes NF-kappa-B activation (PubMed:28481331, PubMed:34012115). Together with OTULIN, the LUBAC complex regulates the canonical Wnt signaling during angiogenesis (PubMed:23708998). RNF31 is required for linear ubiquitination of BCL10, thereby promoting TCR-induced NF-kappa-B activation (PubMed:27777308). Binds polyubiquitin of different linkage types (PubMed:23708998). [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) which consists of SHARPIN, RBCK1 and RNF31 (PubMed:17006537, PubMed:21455173, PubMed:21455180, PubMed:21455181, PubMed:28481331). LUBAC has a MW of approximately 600 kDa suggesting a heteromultimeric assembly of its subunits (PubMed:17006537, PubMed:21455173, PubMed:21455180, PubMed:21455181). Associates with the TNF-R1 signaling complex (TNF-RSC) in a stimulation-dependent manner (PubMed:20005846). Interacts (via the PUB domain) with OTULIN (via the PIM motif); the interaction is direct (PubMed:23708998, PubMed:24726323, PubMed:24726327). Interacts (via the PUB domain) with VCP (via the PIM motif) (PubMed:24726327). Interacts (via the PUB domain) with SPATA2 (via the PIM motif); interaction is direct and bridges RNF31 and CYLD (PubMed:27458237, PubMed:27545878, PubMed:28189684, PubMed:27591049). Interacts with CYLD; the interaction is indirect and is mediated via SPATA2 (PubMed:27458237, PubMed:27545878, PubMed:26997266). Interacts with MUSK (By similarity). Interacts with CARD11, promoting linear ubiquitination of BCL10 (PubMed:27777308). (Microbial infection) Interacts with S.flexneri E3 ubiquitin-protein ligases IpaH1.4 and IpaH2.5, leading to its ubiquitination. Expressed in both normal and transformed breast epithelial cell lines. The PUB domain mediates interaction with the PIM motifs of VCP and RNF31, with a strong preference for RNF31. The RanBP2-type zinc fingers mediate the specific interaction with ubiquitin. The UBA domain mediates association with RBCK1/HOIL1 via interaction with its UBL domain. RING 1 and IBR zinc-fingers catalyze the first step transfer of ubiquitin from the E2 onto RING 2, to transiently form a HECT-like covalent thioester intermediate. The linear ubiquitin chain determining domain (LDD) mediates the final transfer of ubiquitin from RING 2 onto the N-terminus of a target ubiquitin. Autoubiquitinated (PubMed:24726323). Interaction with OTULIN is required to suppress formation of 'Met-1'-linked polyubiquitin chains and prevent subsequent inactivation of the LUBAC complex (PubMed:24726323). Cleaved by caspase during apoptosis. (Microbial infection) Ubiquitinated by S.flexneri E3 ubiquitin-protein ligases IpaH1.4 and IpaH2.5, leading to its degradation by the proteasome, thereby preventing formation of the bacterial ubiquitin coat and activation of innate immunity. Belongs to the RBR family. Truncated C-terminus. Intron retention.