Helical wheel depiction of the self-association unit.

The predicted structure of the normal spectrin self-association unit was examined for the presence of various types of noncovalent interactions, based on their chemical characteristics and proximity. These interactions are depicted and are summarized in Table 2. Note that nearly all of the interactions stabilizing the triple helical self-association unit arise between helix A or B with helix C. One interaction between helix A and B involves a salt bridge with R2079 (labeled), which falls in the loop sequence between helix B and C. Helices A and B are derived from β-spectrin (shaded), helix C from α-spectrin.