3f31
Crystal Structure of the N-terminal region of AlphaII-spectrin Tetramerization Domain
Structural highlights
DiseaseSPTN1_HUMAN West syndrome. The disease is caused by mutations affecting the gene represented in this entry. FunctionSPTN1_HUMAN Fodrin, which seems to be involved in secretion, interacts with calmodulin in a calcium-dependent manner and is thus candidate for the calcium-dependent movement of the cytoskeleton at the membrane. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedWe have solved the crystal structure of a segment of nonerythroid alpha-spectrin (alphaII) consisting of the first 147 residues to a resolution of 2.3 A. We find that the structure of this segment is generally similar to a corresponding segment from erythroid alpha-spectrin (alphaI) but exhibits unique differences with functional significance. Specific features include the following: (i) an irregular and frayed first helix (Helix C'); (ii) a helical conformation in the junction region connecting Helix C' with the first structural domain (D1); (iii) a long A(1)B(1) loop in D1; and (iv) specific inter-helix hydrogen bonds/salt bridges that stabilize D1. Our findings suggest that the hydrogen bond networks contribute to structural domain stability, and thus rigidity, in alphaII, and the lack of such hydrogen bond networks in alphaI leads to flexibility in alphaI. We have previously shown the junction region connecting Helix C' to D1 to be unstructured in alphaI (Park, S., Caffrey, M. S., Johnson, M. E., and Fung, L. W. (2003) J. Biol. Chem. 278, 21837-21844) and now find it to be helical in alphaII, an important difference for alpha-spectrin association with beta-spectrin in forming tetramers. Homology modeling and molecular dynamics simulation studies of the structure of the tetramerization site, a triple helical bundle of partial domain helices, show that mutations in alpha-spectrin will affect Helix C' structural flexibility and/or the junction region conformation and may alter the equilibrium between spectrin dimers and tetramers in cells. Mutations leading to reduced levels of functional tetramers in cells may potentially lead to abnormal neuronal functions. Crystal structure of the nonerythroid alpha-spectrin tetramerization site reveals differences between erythroid and nonerythroid spectrin tetramer formation.,Mehboob S, Song Y, Witek M, Long F, Santarsiero BD, Johnson ME, Fung LW J Biol Chem. 2010 May 7;285(19):14572-84. Epub 2010 Mar 14. PMID:20228407[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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