Spectrin beta 1: Proteins and Enzymes

Spectrin (Sp), the most abundant of the erythrocyte membrane skeleton proteins, helps these cells maintain their characteristic biconcave shape while remaining flexible and elastic. Erythrocyte Sp is a heterodimer composed of a 280 kDa alpha subunit and a 246 kDa beta subunit which associate in a side-to-side, antiparallel configuration to form a 100 nm rod-like structure. Sp in other tissues may be composed of distinct but homologous alpha and beta subunits, sometimes referred to as fodrin. A newly introduced nomenclature designates the Sp subunits of the erythrocyte as alpha-1 and beta-1, and the fodrin subunits as alpha-2 and beta-2. Alternatively spliced forms of each are designated as epsilon-1, epsilon-2, etc. (e.g. beta-1 epsilon-1).