The horizontal linkages between spectrin-spectrin dimers and between spectrin, actin, and protein 4.1R in the junctional complex in the spectrin-based membrane skeleton. The repeats of α-spectrin are colored gray while those of β-spectrin are colored light green. The single helical repeat at N-terminus of α-spectrin of 1 dimer interacts with the 2 helical repeat at C-terminus of β-spectrin of the second dimer to constitute spectrin dimer-dimer interaction indicated in pink. The PS binding spectrin repeats are colored in dark blue while repeats with low thermal stability (Tm < 37°C) are shown in red. The various components of the junctional complex at the end of spectrin dimer are also shown. EF hands at C-terminus of α-spectrin and the actin-binding domain (ABD) at N-terminus of β-spectrin are also indicated. Illustration by Paulette Dennis.