Comparison with other spectrin structures shows that the composite 3-helix bundle recapitulates a spectrin repeat. (A) Comparison of human erythroid spectrin repeats α0-1 from the crystal structure of the complex (α0-1, blue) to the structure of α0-1 in solution (purple)39 and to a crystal structure of human brain α0-1 spectrin (green)42 indicates stabilization of the helical linker between repeats 0 and 1 in the head-to-head α/β complex. In contrast to the NMR structure and crystal structure, the entirety of the repeat α0 is helical when in complex with β16-17. (B) Superposition of the structure of the tetramerization domain (blue and yellow) with the 3-repeat structure of human brain β-spectrin repeats 14-16 (red)32 demonstrate that the composite repeat highly resembles an intact spectrin repeat.
