Pascual J, Pfuhl M, Walther D, Saraste M, Nilges M. Solution structure of the spectrin repeat: a left-handed antiparallel triple-helical coiled-coil.
J Mol Biol 1997;
273:740-51. [PMID:
9356261 DOI:
10.1006/jmbi.1997.1344]
[Citation(s) in RCA: 134] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Cytoskeletal proteins belonging to the spectrin family have an elongated structure composed of repetitive units. The three-dimensional solution structure of the 16th repeat from chicken brain alpha-spectrin (R16) has been determined by NMR spectroscopy and distance geometry-simulated annealing calculations. We used a total of 1035 distance restraints, which included 719 NOE-based values obtained by applying the ambiguous restraints for iterative assignment (ARIA) method. In addition, we performed a direct refinement against 1H-chemical shifts. The final ensemble of 20 structures shows an average RMSD of 1.52 A from the mean for the backbone atoms, excluding loops and N and C termini. R16 is made up of three antiparallel alpha-helices separated by two loops, and folds into a left-handed coiled-coil. The basic unit of spectrin is an antiparallel heterodimer composed of two homologous chains, beta and alpha. These assemble a tetramer via a mechanism that relies on the completion of a single repeat by association of the partial repeats located at the C terminus of the beta-chain (two helices) and at the N terminus of the alpha-chain (one helix). This tetramer is the assemblage able to cross-link actin filaments. Model building by homology of the "tetramerization" repeat from human erythrocyte spectrin illuminates the possible role of point mutations which cause hemolytic anemias.
Collapse