About TAGLN / Transgelin:
TAGLN, which stands for transgelin-related protein, was first identified in TAG-1 cells and TAG-2 cells. TAGLN is a transmembrane glycoprotein that contains an amino acid sequence (RHWY) at its extracellular N terminus, cell adhesion domains containing the RGD motif on its extracellular C terminus, and six to seven leucine-rich motifs.
TAGLN proteins are composed of 11-16 kDa TAGLN repeats. TAGLNs have been identified in human, rat, and mouse TAGLN proteins (TAGLN1, TAGLN2, and TAG), with the TAGLN3 gene being located on chromosome X. TAG proteins contain multiple regions, including an N-terminal coiled-coil region which is used for oligomerization to form TAGs.
TAG tags are found on the cytoplasmic tails of transmembrane receptors via interactions with calcium ions. TAG family members may dimerize or oligomerize to form paracrystalline structures such as helical filaments or fibrils. Each helical filament can be composed of TAGLN monomers, TAGLN dimers, or TAGLN oligomers. TAG proteins can act as a scaffold to position and guide other components of the cell membrane. TAGs may also have roles in cytoskeletal polymerization, signal transduction, and calcium ion homeostasis. TAG phosphorylation sites are located at the TAG 2A/2B domains, which are defined based on their distance from the C -terminus.
TAGLNs have been identified in human TAGLN1 protein (Transgelin), rat TAGLN2 protein (Transthyretin) and mouse TAGLN3 protein (Transgelin). TAG proteins containing four repeats were observed to form hexagonal arrays, TAG proteins containing seven repeats formed octahedral arrays, and TAGLN3 proteins containing 11-16 TAGLNs formed icosahedral structures. TAGLN2 protein is found in the endoplasmic reticulum of cells, where it serves as a carrier for TTR -binding thyroid hormones. TAGLN1 contains a C -terminal signal peptide sequence suggesting that TAGLN1 may be secreted from the cell.