Solution Structural Studies on Human Erythrocyte Alpha Spectrin N Terminal Tetramerization Domain
[SPTA1_HUMAN] Defects in SPTA1 are the cause of elliptocytosis type 2 (EL2) [MIM:130600]. EL2 is a Rhesus-unlinked form of hereditary elliptocytosis, a genetically heterogeneous, autosomal dominant hematologic disorder. It is characterized by variable hemolytic anemia and elliptical or oval red cell shape.            Defects in SPTA1 are a cause of hereditary pyropoikilocytosis (HPP) [MIM:266140]. HPP is an autosomal recessive disorder characterized by hemolytic anemia, microspherocytosis, poikilocytosis, and an unusual thermal sensitivity of red cells. Defects in SPTA1 are the cause of spherocytosis type 3 (SPH3) [MIM:270970]; also known as hereditary spherocytosis type 3 (HS3). Spherocytosis is a hematologic disorder leading to chronic hemolytic anemia and characterized by numerous abnormally shaped erythrocytes which are generally spheroidal. SPH3 is characterized by severe hemolytic anemia. Inheritance is autosomal recessive.
[SPTA1_HUMAN] Spectrin is the major constituent of the cytoskeletal network underlying the erythrocyte plasma membrane. It associates with band 4.1 and actin to form the cytoskeletal superstructure of the erythrocyte plasma membrane.
Publication Abstract from PubMed
We have determined the solution NMR structure of a recombinant peptide that consists of the first 156 residues of erythroid alpha-spectrin. The first 20 residues preceding the first helix (helix C') are in a disordered conformation. The subsequent three helices (helices A1, B1, and C1) form a triple helical bundle structural domain that is similar, but not identical, to previously published structures for spectrin from Drosophila and chicken brain. Paramagnetic spin label-induced NMR resonance broadening shows that helix C', the partial domain involved in alpha- and beta-spectrin association, exhibits little interaction with the structural domain. Surprisingly, helix C' is connected to helix A1 of the structural domain by a segment of 7 residues (the junction region) that exhibits a flexible disordered conformation, in contrast to the predicted rigid helical structure. We suggest that the flexibility of this particular junction region may play an important role in modulating the association affinity of alpha- and beta-spectrin at the tetramerization site of different isoforms, such as erythroid spectrin and brain spectrin. These findings may provide insight for explaining various physiological and pathological conditions that are a consequence of varying alpha- and beta-subunit self-association affinities in their formation of the various spectrin tetramers.
Solution structural studies on human erythrocyte alpha-spectrin tetramerization site.,Park S, Caffrey MS, Johnson ME, Fung LW J Biol Chem. 2003 Jun 13;278(24):21837-44. Epub 2003 Apr 1. PMID:12672815
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