Tetraspanin, extracellular domain or large extracellular loop (LEL), peripherin_like family. Tetraspanins are trans-membrane proteins with 4 trans-membrane segments. Both the N- and C-termini lie on the intracellular side of the membrane. This alignment model spans the extracellular domain between the 3rd and 4th trans-membrane segment. Tetraspanins are involved in diverse processes and their various functions may relate to their ability to act as molecular facilitators. Tetraspanins associate laterally with one another and cluster dynamically with numerous parnter domains in membrane microdomains, forming a network of multimolecular complexes, the "tetraspanin web". Peripherin, or RDS (retinal degradation slow) is a glycoprotein expressed in vertebrate photoreceptors, located at the rim of the disc membranes of the photoreceptor outer segments. RDS is thought to play a major role in folding and stacking of the discs. Mutations in RDS have been linked to hereditary retinal dystrophies, which typically exhibit a wide phenotypic spectrum.
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