We decided not to include type III IFNs in our study since, despite binding to distinct receptors from those of type I IFNs, type III IFNs induce antiviral activity using the same signaling pathway, the same IFN-stimulated response elements (ISREs), and lead to the induction of almost the same IFN-stimulated genes (ISGs) than type I (α and β) IFNs [18], [41].
However, the mechanisms that dictate the tissue-specificity of Twist1 binding to distinct transcriptional targets in different cell types remain to be determined.
Ligands binding to distinct epitopes of anchoring molecules may enter cells differently.
After being cleaved at a site proximal to the transmembrane domain of TNF-α by TNF-α converting enzyme, a soluble trimeric form of TNF-α is released and exerts its activity by binding to two structurally distinct type I and type II TNF receptors (TNFRI and TNFRII) on effector cells.
While Ig domains are prominently known for the ability to mediate the binding of signaling peptides, also LRR motifs have been described to act as adaptor molecules for the binding of distinct types of signaling ligand peptides in a variety of proteins (Kobe and Deisenhofer 1994; Buchanan and Gay 1996), including Tyrosine Kinase Receptors (Windisch et al. 1995a; Windisch et al. 1995b).
Once activated, mature TGF-β initiates transmembrane signaling by binding to two distinct transmembrane Ser/Thr protein kinases, termed TGF-β type I (TβR-I) and type II (TβR-II) receptors (23 25).
Based on morphology, vital dye binding and immunocytochemistry, distinct types of epidermal or branchial ICs have been reported in diverse fish species, and have been suggested to mediate an equivalent function as their counterparts in the kidneys of terrestrial vertebrates [9], [10].
PGE2 exerts its biological functions via binding to four types of G-protein-coupled receptors termed EP1-4 [ 13, 14], which couple to distinct downstream second messenger systems.
Here, all antibodies except PaD213-A5 showed no predominant binding to any distinct form.
