Spectrin

Spectrin is the major component of the protein network, which covers the cytoplasmic surface of vertebrate erythrocyte membranes. It is a high molecular weight heterodimer composed of two subunits (molecular weights of approximately 230 kDa and 250 kDa). Spectrins are extended flexible molecules approximately 200-260 nm in length and 3-6 nm across with actin-binding domains at each end. Spectrins are composed of α and β subunits, which are both related to α-actinin. The α and β subunits associate laterally to form antiparallel heterodimers and the heterodimers are assembled head-head to form heterotetramers. The erythrocyte membrane skeleton is organized as a polygonal network formed by five to seven extended spectrin molecules linked to short actin filaments approximately 40 nm in length. The spectrin-actin network of erythrocytes is coupled to the membrane bilayer primarily through the association of spectrin with ankyrin, which in turn is bound to the cytoplasmic domain of the anion exchanger. A major function of the spectrin skeleton in erythrocytes is to provide mechanical support for the membrane bilayer and allow survival of the cells in circulation. 

Spectrin Products

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