Comparison of evolutionary sequence conservation within the spectrin α0 C-helix. Alignments of spectrin sequences encompassing approximately the C-helix of the α0 partial repeat involved in tetramer binding are shown. All known N-terminal region sequences of α-spectrins were extracted from the National Center for Biotechnology Information nonredundant protein sequence database⁶⁴  using BLASTP 2.2.17 and human red cell spectrin (SPTA1) residues 1 to 158 as the query sequence. The severity of decreased tetramer binding affinity (Table 1) and residue numbers of the 14 known HE/HPP mutations are shown above the sequences. For these positions, residues that match the wild-type human red cell spectrin sequence are shown in bold type.