TIRdomain

The TIR domain is a protein domain found in a variety of eukaryotic and prokaryotic proteins. It is named after the Toll-interleukin-1 receptor (TIR) superfamily, to which many of its characterized members belong. This domain is characterized by a conserved alpha-helical structure and is typically found in the intracellular region of proteins involved in signal transduction.

In eukaryotes, TIR domains are prominently featured in proteins of the innate immune system. For example, they are present in Toll-like receptors (TLRs), which recognize conserved microbial molecules and initiate inflammatory responses. They are also found in adaptor proteins like MyD88 and Mal, which mediate signal transmission downstream of TLRs. The interaction between TIR domains is crucial for assembling signaling complexes that activate transcription factors such as NF-κB.

In plants, TIR domains are also important components of disease resistance proteins (R proteins). These R proteins often recognize pathogen effectors and trigger defense responses, a process mediated by the intracellular TIR domains. The specific mechanisms of TIR domain function can vary depending on the protein and organism, but often involve protein-protein interactions to propagate signaling cascades. Prokaryotic proteins containing TIR domains have been identified in various contexts, including bacterial virulence factors and regulatory proteins.