beta-trefoil domain found in interleukin-18 (IL-18) and similar proteins
IL-18, also called Iboctadekin, or interferon gamma-inducing factor, or IFN-gamma-inducing factor, or interleukin-1 gamma, or IL-1 gamma, is a proinflammatory cytokine primarily involved in polarized T-helper 1 (Th1) cell and natural killer (NK) cell immune responses. Upon binding to IL18R1 and IL18RAP, it forms a signaling ternary complex which activates NF-kappa-B, triggering synthesis of inflammatory mediators. IL-18 works synergistically with IL12/interleukin-12 to induce IFN-gamma synthesis from Th1 cells and natural killer (NK) cells. IL-18 contains a beta-trefoil domain, which is characterized by 12 beta strands folded into three similar trefoil subdomains (alpha, beta, and gamma) associated to give an overall structure with pseudo-3-fold symmetry.
Jiyao W et al.(2023). "The conserved domain database in 2023.",