The spectrin tetramerization domains show multiple, highly conserved surfaces. (A) The interacting surfaces of α0-1 and β16-17 show regions of relatively high conservation. This is especially notable in comparing repeat β16 (mostly blue) to the partial repeat β17 (mostly red). As in previous figures, the interacting surfaces of both molecules are opened to face the reader. (B) Conservation analysis of the assembled tetramerization domain displays one surface with markedly greater conservation than the other, which may present a biologically relevant interaction surface. The conservation maps presented were generated using sequences and alignments derived by the Consurf database.28 An additional analysis with manually selected and aligned sequences yielded similar findings.