Primary structure of the brain alpha-spectrin [published erratum appears in J Cell Biol 1989 Mar;108(3):following 1175]

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Abstract
We have determined the nucelotide sequence coding for the chicken brain .alpha.-spectrin. It is derived both from the cDNA and genomic sequences, comprises the entire coding frame, 5'' and 3'' untranslated sequences, and terminates in the poly(A)-tail. The deduced amino acid sequence was used to map the domain structure of the protein. The .alpha.-chain of brain spectrin contains 22 segments of which 20 correspond to the repeat of the human erythrocyte spectrin (Speicher, D. W., and V. T. Marchesi. 1984. Nature (Lond.). 311:177-180.), typically made of 106 residues. These homologous segments probably account for the flexible, rod-like structure of spectrin. Secondary structure prediction suggests predominantly .alpha.-helical structure for the entire chain. Parts of the primary structure are excluded from the repetitive pattern and they reside in the middle part of the sequence and in its COOH terminus. Search for homology in other proteins showed the presence of the following distinct structures in these nonrepetitive regions: (a) the COOH-terminal part of the molecule that shows homology with .alpha.-actinin, (b) two typical EF-hand (i.e., Ca2+-binding) structures in this region, (c) a sequence close to the EF-hand that fulfills the criteria for a calmodulin-binding site, and (d) a domain in the middle of the sequence that is homologous to a NH2-terminal segment of several src-tyrosine kinases and to a domain of phospholipase C. These regions are good candidates to carry some established as well as some yet unestablished functions of spectrin. Comparative analysis showed that .alpha.-spectrin is well conserved across the species boundaries from Xenopus to man, and that the human erythrocyte .alpha.-spectrin is divergent from the other spectrins.