Interleukin-1 beta (IL1 beta or IL1B) also known as catabolin, is a member of the interleukin 1 cytokine family. IL1 is a name that designates two pleiotropic cytokines, IL-1 alpha (IL-1F1) and IL-1 beta (IL-1F2), which are the products of distinct genes. IL-1 alpha and IL-1 beta are structurally related polypeptides that share approximately 21% amino acid (aa) identity in human. Both proteins are produced by a wide variety of cells in response to inflammatory agents, infections, or microbial endotoxins. While IL-1 alpha and IL-1 beta are regulated independently, they bind to the same receptor and exert identical biological effects. IL-1RI binds directly to IL-1 alpha or IL-1 beta and then associates with IL-1R accessory protein (IL-1R3/IL-1RAcP) to form a high-affinity receptor complex that is competent for signal transduction. IL-1RII has high affinity for IL-1 beta but functions as a decoy receptor and negative regulator of IL-1 beta activity. The human IL-1 beta cDNA encodes a 269 aa precursor. A 116 aa propeptide is cleaved intracellularly by the cysteine protease IL-1 beta converting enzyme (Caspase-1/ICE) to generate the active cytokine [5-7]. The 17 kDa mature human IL-1 beta shares 96% aa sequence identity with rhesus and 67%-78% with canine, cotton rat, equine, feline, mouse, porcine, and rat IL-1 beta.
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