Spectrin oligomers: A structural feature of the erythrocyte cytoskeleton

Spectrin reversibly self-associates to high molecular weight oligomers through a concentration-driven process characterized by association constants of about 10⁵ mol^?1. This association is prominent under physiological conditions of pH, ionic strength, and temperature. It is disrupted by urea, but not Triton X-100. The process of spectrin association appears mathematically to resemble that for tropomyosin, although the mechanism is probably different. Spectrin association is weak compared to other prominent protein–protein associations in the red cell membrane skeleton. The linkage of these weak and strong associations suggests a process whereby the membrane skelton spontaneously assembles. Such affinity-modulated assembly involving weak associations is likely to be the focus of numerous membrane control mechanisms.